1<!DOCTYPE html> 2<html lang="en"> 3<head> 4 <meta charset="utf-8"> 5 <meta name="viewport" content="width=device-width"> 6 <meta name="nodejs.org:node-version" content="v18.20.1"> 7 <title>Modules: Packages | Node.js v18.20.1 Documentation</title> 8 <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Lato:400,700,400italic&display=fallback"> 9 <link rel="stylesheet" href="assets/style.css"> 10 <link rel="stylesheet" href="assets/hljs.css"> 11 <link rel="canonical" href="https://nodejs.org/api/packages.html"> 12 <script async defer src="assets/api.js" type="text/javascript"></script> 13 14</head> 15<body class="alt apidoc" id="api-section-packages"> 16 <div id="content" class="clearfix"> 17 <div id="column2" class="interior"> 18 <div id="intro" class="interior"> 19 <a href="/" title="Go back to the home page"> 20 Node.js 21 </a> 22 </div> 23 <ul> 24<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 25<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 26</ul> 27<hr class="line"> 28<ul> 29<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 30<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 31<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 32<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 33<li><a href="addons.html" class="nav-addons">C++ addons</a></li> 34<li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> 35<li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> 36<li><a href="child_process.html" class="nav-child_process">Child processes</a></li> 37<li><a href="cluster.html" class="nav-cluster">Cluster</a></li> 38<li><a href="cli.html" class="nav-cli">Command-line options</a></li> 39<li><a href="console.html" class="nav-console">Console</a></li> 40<li><a href="corepack.html" class="nav-corepack">Corepack</a></li> 41<li><a href="crypto.html" class="nav-crypto">Crypto</a></li> 42<li><a href="debugger.html" class="nav-debugger">Debugger</a></li> 43<li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> 44<li><a href="diagnostics_channel.html" class="nav-diagnostics_channel">Diagnostics Channel</a></li> 45<li><a href="dns.html" class="nav-dns">DNS</a></li> 46<li><a href="domain.html" class="nav-domain">Domain</a></li> 47<li><a href="errors.html" class="nav-errors">Errors</a></li> 48<li><a href="events.html" class="nav-events">Events</a></li> 49<li><a href="fs.html" class="nav-fs">File system</a></li> 50<li><a href="globals.html" class="nav-globals">Globals</a></li> 51<li><a href="http.html" class="nav-http">HTTP</a></li> 52<li><a href="http2.html" class="nav-http2">HTTP/2</a></li> 53<li><a href="https.html" class="nav-https">HTTPS</a></li> 54<li><a href="inspector.html" class="nav-inspector">Inspector</a></li> 55<li><a href="intl.html" class="nav-intl">Internationalization</a></li> 56<li><a href="modules.html" class="nav-modules">Modules: CommonJS modules</a></li> 57<li><a href="esm.html" class="nav-esm">Modules: ECMAScript modules</a></li> 58<li><a href="module.html" class="nav-module">Modules: <code>node:module</code> API</a></li> 59<li><a href="packages.html" class="nav-packages active">Modules: Packages</a></li> 60<li><a href="net.html" class="nav-net">Net</a></li> 61<li><a href="os.html" class="nav-os">OS</a></li> 62<li><a href="path.html" class="nav-path">Path</a></li> 63<li><a href="perf_hooks.html" class="nav-perf_hooks">Performance hooks</a></li> 64<li><a href="permissions.html" class="nav-permissions">Permissions</a></li> 65<li><a href="process.html" class="nav-process">Process</a></li> 66<li><a href="punycode.html" class="nav-punycode">Punycode</a></li> 67<li><a href="querystring.html" class="nav-querystring">Query strings</a></li> 68<li><a href="readline.html" class="nav-readline">Readline</a></li> 69<li><a href="repl.html" class="nav-repl">REPL</a></li> 70<li><a href="report.html" class="nav-report">Report</a></li> 71<li><a href="single-executable-applications.html" class="nav-single-executable-applications">Single executable applications</a></li> 72<li><a href="stream.html" class="nav-stream">Stream</a></li> 73<li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> 74<li><a href="test.html" class="nav-test">Test runner</a></li> 75<li><a href="timers.html" class="nav-timers">Timers</a></li> 76<li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> 77<li><a href="tracing.html" class="nav-tracing">Trace events</a></li> 78<li><a href="tty.html" class="nav-tty">TTY</a></li> 79<li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> 80<li><a href="url.html" class="nav-url">URL</a></li> 81<li><a href="util.html" class="nav-util">Utilities</a></li> 82<li><a href="v8.html" class="nav-v8">V8</a></li> 83<li><a href="vm.html" class="nav-vm">VM</a></li> 84<li><a href="wasi.html" class="nav-wasi">WASI</a></li> 85<li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li> 86<li><a href="webstreams.html" class="nav-webstreams">Web Streams API</a></li> 87<li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> 88<li><a href="zlib.html" class="nav-zlib">Zlib</a></li> 89</ul> 90<hr class="line"> 91<ul> 92<li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 93</ul> 94 </div> 95 96 <div id="column1" data-id="packages" class="interior"> 97 <header class="header"> 98 <div class="header-container"> 99 <h1>Node.js v18.20.1 documentation</h1> 100 <button class="theme-toggle-btn" id="theme-toggle-btn" title="Toggle dark mode/light mode" aria-label="Toggle dark mode/light mode" hidden> 101 <svg xmlns="http://www.w3.org/2000/svg" class="icon dark-icon" height="24" width="24"> 102 <path fill="none" d="M0 0h24v24H0z" /> 103 <path d="M11.1 12.08c-2.33-4.51-.5-8.48.53-10.07C6.27 2.2 1.98 6.59 1.98 12c0 .14.02.28.02.42.62-.27 1.29-.42 2-.42 1.66 0 3.18.83 4.1 2.15A4.01 4.01 0 0111 18c0 1.52-.87 2.83-2.12 3.51.98.32 2.03.5 3.11.5 3.5 0 6.58-1.8 8.37-4.52-2.36.23-6.98-.97-9.26-5.41z"/> 104 <path d="M7 16h-.18C6.4 14.84 5.3 14 4 14c-1.66 0-3 1.34-3 3s1.34 3 3 3h3c1.1 0 2-.9 2-2s-.9-2-2-2z"/> 105 </svg> 106 <svg xmlns="http://www.w3.org/2000/svg" class="icon light-icon" height="24" width="24"> 107 <path d="M0 0h24v24H0z" fill="none" /> 108 <path d="M6.76 4.84l-1.8-1.79-1.41 1.41 1.79 1.79 1.42-1.41zM4 10.5H1v2h3v-2zm9-9.95h-2V3.5h2V.55zm7.45 3.91l-1.41-1.41-1.79 1.79 1.41 1.41 1.79-1.79zm-3.21 13.7l1.79 1.8 1.41-1.41-1.8-1.79-1.4 1.4zM20 10.5v2h3v-2h-3zm-8-5c-3.31 0-6 2.69-6 6s2.69 6 6 6 6-2.69 6-6-2.69-6-6-6zm-1 16.95h2V19.5h-2v2.95zm-7.45-3.91l1.41 1.41 1.79-1.8-1.41-1.41-1.79 1.8z"/> 109 </svg> 110 </button> 111 </div> 112 <div id="gtoc"> 113 <ul> 114 <li class="pinned-header">Node.js v18.20.1</li> 115 116 <li class="picker-header"> 117 <a href="#"> 118 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 119 Table of contents 120 </a> 121 122 <div class="picker"><div class="toc"><ul> 123<li><a href="#modules-packages">Modules: Packages</a> 124<ul> 125<li><a href="#introduction">Introduction</a></li> 126<li><a href="#determining-module-system">Determining module system</a> 127<ul> 128<li><a href="#introduction_1">Introduction</a></li> 129<li><a href="#modules-loaders">Modules loaders</a></li> 130<li><a href="#packagejson-and-file-extensions"><code>package.json</code> and file extensions</a></li> 131<li><a href="#--input-type-flag"><code>--input-type</code> flag</a></li> 132</ul> 133</li> 134<li><span class="stability_1"><a href="#determining-package-manager">Determining package manager</a></span></li> 135<li><a href="#package-entry-points">Package entry points</a> 136<ul> 137<li><a href="#main-entry-point-export">Main entry point export</a></li> 138<li><a href="#subpath-exports">Subpath exports</a> 139<ul> 140<li><a href="#extensions-in-subpaths">Extensions in subpaths</a></li> 141</ul> 142</li> 143<li><a href="#exports-sugar">Exports sugar</a></li> 144<li><a href="#subpath-imports">Subpath imports</a></li> 145<li><a href="#subpath-patterns">Subpath patterns</a></li> 146<li><a href="#conditional-exports">Conditional exports</a></li> 147<li><a href="#nested-conditions">Nested conditions</a></li> 148<li><a href="#resolving-user-conditions">Resolving user conditions</a></li> 149<li><a href="#community-conditions-definitions">Community Conditions Definitions</a></li> 150<li><a href="#self-referencing-a-package-using-its-name">Self-referencing a package using its name</a></li> 151</ul> 152</li> 153<li><a href="#dual-commonjses-module-packages">Dual CommonJS/ES module packages</a> 154<ul> 155<li><a href="#dual-package-hazard">Dual package hazard</a></li> 156<li><a href="#writing-dual-packages-while-avoiding-or-minimizing-hazards">Writing dual packages while avoiding or minimizing hazards</a> 157<ul> 158<li><a href="#approach-1-use-an-es-module-wrapper">Approach #1: Use an ES module wrapper</a></li> 159<li><a href="#approach-2-isolate-state">Approach #2: Isolate state</a></li> 160</ul> 161</li> 162</ul> 163</li> 164<li><a href="#nodejs-packagejson-field-definitions">Node.js <code>package.json</code> field definitions</a> 165<ul> 166<li><a href="#name"><code>"name"</code></a></li> 167<li><a href="#main"><code>"main"</code></a></li> 168<li><span class="stability_1"><a href="#packagemanager"><code>"packageManager"</code></a></span></li> 169<li><a href="#type"><code>"type"</code></a></li> 170<li><a href="#exports"><code>"exports"</code></a></li> 171<li><a href="#imports"><code>"imports"</code></a></li> 172</ul> 173</li> 174</ul> 175</li> 176</ul></div></div> 177 </li> 178 179 180 <li class="picker-header"> 181 <a href="#"> 182 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 183 Index 184 </a> 185 186 <div class="picker"><ul> 187<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 188<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 189 190 <li> 191 <a href="index.html">Index</a> 192 </li> 193 </ul> 194 195<hr class="line"> 196<ul> 197<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 198<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 199<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 200<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 201<li><a href="addons.html" class="nav-addons">C++ addons</a></li> 202<li><a href="n-api.html" class="nav-n-api">C/C++ addons with Node-API</a></li> 203<li><a href="embedding.html" class="nav-embedding">C++ embedder API</a></li> 204<li><a href="child_process.html" class="nav-child_process">Child processes</a></li> 205<li><a href="cluster.html" class="nav-cluster">Cluster</a></li> 206<li><a href="cli.html" class="nav-cli">Command-line options</a></li> 207<li><a href="console.html" class="nav-console">Console</a></li> 208<li><a href="corepack.html" class="nav-corepack">Corepack</a></li> 209<li><a href="crypto.html" class="nav-crypto">Crypto</a></li> 210<li><a href="debugger.html" class="nav-debugger">Debugger</a></li> 211<li><a href="deprecations.html" class="nav-deprecations">Deprecated APIs</a></li> 212<li><a href="diagnostics_channel.html" class="nav-diagnostics_channel">Diagnostics Channel</a></li> 213<li><a href="dns.html" class="nav-dns">DNS</a></li> 214<li><a href="domain.html" class="nav-domain">Domain</a></li> 215<li><a href="errors.html" class="nav-errors">Errors</a></li> 216<li><a href="events.html" class="nav-events">Events</a></li> 217<li><a href="fs.html" class="nav-fs">File system</a></li> 218<li><a href="globals.html" class="nav-globals">Globals</a></li> 219<li><a href="http.html" class="nav-http">HTTP</a></li> 220<li><a href="http2.html" class="nav-http2">HTTP/2</a></li> 221<li><a href="https.html" class="nav-https">HTTPS</a></li> 222<li><a href="inspector.html" class="nav-inspector">Inspector</a></li> 223<li><a href="intl.html" class="nav-intl">Internationalization</a></li> 224<li><a href="modules.html" class="nav-modules">Modules: CommonJS modules</a></li> 225<li><a href="esm.html" class="nav-esm">Modules: ECMAScript modules</a></li> 226<li><a href="module.html" class="nav-module">Modules: <code>node:module</code> API</a></li> 227<li><a href="packages.html" class="nav-packages active">Modules: Packages</a></li> 228<li><a href="net.html" class="nav-net">Net</a></li> 229<li><a href="os.html" class="nav-os">OS</a></li> 230<li><a href="path.html" class="nav-path">Path</a></li> 231<li><a href="perf_hooks.html" class="nav-perf_hooks">Performance hooks</a></li> 232<li><a href="permissions.html" class="nav-permissions">Permissions</a></li> 233<li><a href="process.html" class="nav-process">Process</a></li> 234<li><a href="punycode.html" class="nav-punycode">Punycode</a></li> 235<li><a href="querystring.html" class="nav-querystring">Query strings</a></li> 236<li><a href="readline.html" class="nav-readline">Readline</a></li> 237<li><a href="repl.html" class="nav-repl">REPL</a></li> 238<li><a href="report.html" class="nav-report">Report</a></li> 239<li><a href="single-executable-applications.html" class="nav-single-executable-applications">Single executable applications</a></li> 240<li><a href="stream.html" class="nav-stream">Stream</a></li> 241<li><a href="string_decoder.html" class="nav-string_decoder">String decoder</a></li> 242<li><a href="test.html" class="nav-test">Test runner</a></li> 243<li><a href="timers.html" class="nav-timers">Timers</a></li> 244<li><a href="tls.html" class="nav-tls">TLS/SSL</a></li> 245<li><a href="tracing.html" class="nav-tracing">Trace events</a></li> 246<li><a href="tty.html" class="nav-tty">TTY</a></li> 247<li><a href="dgram.html" class="nav-dgram">UDP/datagram</a></li> 248<li><a href="url.html" class="nav-url">URL</a></li> 249<li><a href="util.html" class="nav-util">Utilities</a></li> 250<li><a href="v8.html" class="nav-v8">V8</a></li> 251<li><a href="vm.html" class="nav-vm">VM</a></li> 252<li><a href="wasi.html" class="nav-wasi">WASI</a></li> 253<li><a href="webcrypto.html" class="nav-webcrypto">Web Crypto API</a></li> 254<li><a href="webstreams.html" class="nav-webstreams">Web Streams API</a></li> 255<li><a href="worker_threads.html" class="nav-worker_threads">Worker threads</a></li> 256<li><a href="zlib.html" class="nav-zlib">Zlib</a></li> 257</ul> 258<hr class="line"> 259<ul> 260<li><a href="https://github.com/nodejs/node" class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 261</ul></div> 262 </li> 263 264 265 <li class="picker-header"> 266 <a href="#"> 267 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 268 Other versions 269 </a> 270 <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v21.x/api/packages.html">21.x</a></li> 271<li><a href="https://nodejs.org/docs/latest-v20.x/api/packages.html">20.x <b>LTS</b></a></li> 272<li><a href="https://nodejs.org/docs/latest-v19.x/api/packages.html">19.x</a></li> 273<li><a href="https://nodejs.org/docs/latest-v18.x/api/packages.html">18.x <b>LTS</b></a></li> 274<li><a href="https://nodejs.org/docs/latest-v17.x/api/packages.html">17.x</a></li> 275<li><a href="https://nodejs.org/docs/latest-v16.x/api/packages.html">16.x</a></li> 276<li><a href="https://nodejs.org/docs/latest-v15.x/api/packages.html">15.x</a></li> 277<li><a href="https://nodejs.org/docs/latest-v14.x/api/packages.html">14.x</a></li> 278<li><a href="https://nodejs.org/docs/latest-v13.x/api/packages.html">13.x</a></li> 279<li><a href="https://nodejs.org/docs/latest-v12.x/api/packages.html">12.x</a></li></ol></div> 280 </li> 281 282 <li class="picker-header"> 283 <a href="#"> 284 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 285 Options 286 </a> 287 288 <div class="picker"> 289 <ul> 290 <li> 291 <a href="all.html">View on single page</a> 292 </li> 293 <li> 294 <a href="packages.json">View as JSON</a> 295 </li> 296 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/packages.md">Edit on GitHub</a></li> 297 </ul> 298 </div> 299 </li> 300 </ul> 301 </div> 302 <hr> 303 </header> 304 305 <details id="toc" open><summary>Table of contents</summary><ul> 306<li><a href="#modules-packages">Modules: Packages</a> 307<ul> 308<li><a href="#introduction">Introduction</a></li> 309<li><a href="#determining-module-system">Determining module system</a> 310<ul> 311<li><a href="#introduction_1">Introduction</a></li> 312<li><a href="#modules-loaders">Modules loaders</a></li> 313<li><a href="#packagejson-and-file-extensions"><code>package.json</code> and file extensions</a></li> 314<li><a href="#--input-type-flag"><code>--input-type</code> flag</a></li> 315</ul> 316</li> 317<li><span class="stability_1"><a href="#determining-package-manager">Determining package manager</a></span></li> 318<li><a href="#package-entry-points">Package entry points</a> 319<ul> 320<li><a href="#main-entry-point-export">Main entry point export</a></li> 321<li><a href="#subpath-exports">Subpath exports</a> 322<ul> 323<li><a href="#extensions-in-subpaths">Extensions in subpaths</a></li> 324</ul> 325</li> 326<li><a href="#exports-sugar">Exports sugar</a></li> 327<li><a href="#subpath-imports">Subpath imports</a></li> 328<li><a href="#subpath-patterns">Subpath patterns</a></li> 329<li><a href="#conditional-exports">Conditional exports</a></li> 330<li><a href="#nested-conditions">Nested conditions</a></li> 331<li><a href="#resolving-user-conditions">Resolving user conditions</a></li> 332<li><a href="#community-conditions-definitions">Community Conditions Definitions</a></li> 333<li><a href="#self-referencing-a-package-using-its-name">Self-referencing a package using its name</a></li> 334</ul> 335</li> 336<li><a href="#dual-commonjses-module-packages">Dual CommonJS/ES module packages</a> 337<ul> 338<li><a href="#dual-package-hazard">Dual package hazard</a></li> 339<li><a href="#writing-dual-packages-while-avoiding-or-minimizing-hazards">Writing dual packages while avoiding or minimizing hazards</a> 340<ul> 341<li><a href="#approach-1-use-an-es-module-wrapper">Approach #1: Use an ES module wrapper</a></li> 342<li><a href="#approach-2-isolate-state">Approach #2: Isolate state</a></li> 343</ul> 344</li> 345</ul> 346</li> 347<li><a href="#nodejs-packagejson-field-definitions">Node.js <code>package.json</code> field definitions</a> 348<ul> 349<li><a href="#name"><code>"name"</code></a></li> 350<li><a href="#main"><code>"main"</code></a></li> 351<li><span class="stability_1"><a href="#packagemanager"><code>"packageManager"</code></a></span></li> 352<li><a href="#type"><code>"type"</code></a></li> 353<li><a href="#exports"><code>"exports"</code></a></li> 354<li><a href="#imports"><code>"imports"</code></a></li> 355</ul> 356</li> 357</ul> 358</li> 359</ul></details> 360 361 <div id="apicontent"> 362 <h2>Modules: Packages<span><a class="mark" href="#modules-packages" id="modules-packages">#</a></span><a aria-hidden="true" class="legacy" id="packages_modules_packages"></a></h2> 363 364 365<div class="api_metadata"> 366<details class="changelog"><summary>History</summary> 367<table> 368<tbody><tr><th>Version</th><th>Changes</th></tr> 369<tr><td>v14.13.0, v12.20.0</td> 370<td><p>Add support for <code>"exports"</code> patterns.</p></td></tr> 371<tr><td>v14.6.0, v12.19.0</td> 372<td><p>Add package <code>"imports"</code> field.</p></td></tr> 373<tr><td>v13.7.0, v12.17.0</td> 374<td><p>Unflag conditional exports.</p></td></tr> 375<tr><td>v13.7.0, v12.16.0</td> 376<td><p>Remove the <code>--experimental-conditional-exports</code> option. In 12.16.0, conditional exports are still behind <code>--experimental-modules</code>.</p></td></tr> 377<tr><td>v13.6.0, v12.16.0</td> 378<td><p>Unflag self-referencing a package using its name.</p></td></tr> 379<tr><td>v12.7.0</td> 380<td><p>Introduce <code>"exports"</code> <code>package.json</code> field as a more powerful alternative to the classic <code>"main"</code> field.</p></td></tr> 381<tr><td>v12.0.0</td> 382<td><p>Add support for ES modules using <code>.js</code> file extension via <code>package.json</code> <code>"type"</code> field.</p></td></tr> 383</tbody></table> 384</details> 385</div> 386<section><h3>Introduction<span><a class="mark" href="#introduction" id="introduction">#</a></span><a aria-hidden="true" class="legacy" id="packages_introduction"></a></h3> 387<p>A package is a folder tree described by a <code>package.json</code> file. The package 388consists of the folder containing the <code>package.json</code> file and all subfolders 389until the next folder containing another <code>package.json</code> file, or a folder 390named <code>node_modules</code>.</p> 391<p>This page provides guidance for package authors writing <code>package.json</code> files 392along with a reference for the <a href="#nodejs-packagejson-field-definitions"><code>package.json</code></a> fields defined by Node.js.</p> 393</section><section><h3>Determining module system<span><a class="mark" href="#determining-module-system" id="determining-module-system">#</a></span><a aria-hidden="true" class="legacy" id="packages_determining_module_system"></a></h3> 394<h4>Introduction<span><a class="mark" href="#introduction_1" id="introduction_1">#</a></span><a aria-hidden="true" class="legacy" id="packages_introduction_1"></a></h4> 395<p>Node.js will treat the following as <a href="esm.html">ES modules</a> when passed to <code>node</code> as the 396initial input, or when referenced by <code>import</code> statements or <code>import()</code> 397expressions:</p> 398<ul> 399<li> 400<p>Files with an <code>.mjs</code> extension.</p> 401</li> 402<li> 403<p>Files with a <code>.js</code> extension when the nearest parent <code>package.json</code> file 404contains a top-level <a href="#type"><code>"type"</code></a> field with a value of <code>"module"</code>.</p> 405</li> 406<li> 407<p>Strings passed in as an argument to <code>--eval</code>, or piped to <code>node</code> via <code>STDIN</code>, 408with the flag <code>--input-type=module</code>.</p> 409</li> 410</ul> 411<p>Node.js will treat the following as <a href="modules.html">CommonJS</a> when passed to <code>node</code> as the 412initial input, or when referenced by <code>import</code> statements or <code>import()</code> 413expressions:</p> 414<ul> 415<li> 416<p>Files with a <code>.cjs</code> extension.</p> 417</li> 418<li> 419<p>Files with a <code>.js</code> extension when the nearest parent <code>package.json</code> file 420contains a top-level field <a href="#type"><code>"type"</code></a> with a value of <code>"commonjs"</code>.</p> 421</li> 422<li> 423<p>Strings passed in as an argument to <code>--eval</code> or <code>--print</code>, or piped to <code>node</code> 424via <code>STDIN</code>, with the flag <code>--input-type=commonjs</code>.</p> 425</li> 426</ul> 427<p>Aside from these explicit cases, there are other cases where Node.js defaults to 428one module system or the other based on the value of the 429<a href="cli.html#--experimental-default-typetype"><code>--experimental-default-type</code></a> flag:</p> 430<ul> 431<li> 432<p>Files ending in <code>.js</code> or with no extension, if there is no <code>package.json</code> file 433present in the same folder or any parent folder.</p> 434</li> 435<li> 436<p>Files ending in <code>.js</code> or with no extension, if the nearest parent 437<code>package.json</code> field lacks a <code>"type"</code> field; unless the folder is inside a 438<code>node_modules</code> folder. (Package scopes under <code>node_modules</code> are always treated 439as CommonJS when the <code>package.json</code> file lacks a <code>"type"</code> field, regardless 440of <code>--experimental-default-type</code>, for backward compatibility.)</p> 441</li> 442<li> 443<p>Strings passed in as an argument to <code>--eval</code> or piped to <code>node</code> via <code>STDIN</code>, 444when <code>--input-type</code> is unspecified.</p> 445</li> 446</ul> 447<p>This flag currently defaults to <code>"commonjs"</code>, but it may change in the future to 448default to <code>"module"</code>. For this reason it is best to be explicit wherever 449possible; in particular, package authors should always include the <a href="#type"><code>"type"</code></a> 450field in their <code>package.json</code> files, even in packages where all sources are 451CommonJS. Being explicit about the <code>type</code> of the package will future-proof the 452package in case the default type of Node.js ever changes, and it will also make 453things easier for build tools and loaders to determine how the files in the 454package should be interpreted.</p> 455<h4>Modules loaders<span><a class="mark" href="#modules-loaders" id="modules-loaders">#</a></span><a aria-hidden="true" class="legacy" id="packages_modules_loaders"></a></h4> 456<p>Node.js has two systems for resolving a specifier and loading modules.</p> 457<p>There is the CommonJS module loader:</p> 458<ul> 459<li>It is fully synchronous.</li> 460<li>It is responsible for handling <code>require()</code> calls.</li> 461<li>It is monkey patchable.</li> 462<li>It supports <a href="modules.html#folders-as-modules">folders as modules</a>.</li> 463<li>When resolving a specifier, if no exact match is found, it will try to add 464extensions (<code>.js</code>, <code>.json</code>, and finally <code>.node</code>) and then attempt to resolve 465<a href="modules.html#folders-as-modules">folders as modules</a>.</li> 466<li>It treats <code>.json</code> as JSON text files.</li> 467<li><code>.node</code> files are interpreted as compiled addon modules loaded with 468<code>process.dlopen()</code>.</li> 469<li>It treats all files that lack <code>.json</code> or <code>.node</code> extensions as JavaScript 470text files.</li> 471<li>It cannot be used to load ECMAScript modules (although it is possible to 472<a href="modules.html#the-mjs-extension">load ECMASCript modules from CommonJS modules</a>). When used to load a 473JavaScript text file that is not an ECMAScript module, it loads it as a 474CommonJS module.</li> 475</ul> 476<p>There is the ECMAScript module loader:</p> 477<ul> 478<li>It is asynchronous.</li> 479<li>It is responsible for handling <code>import</code> statements and <code>import()</code> expressions.</li> 480<li>It is not monkey patchable, can be customized using <a href="esm.html#loaders">loader hooks</a>.</li> 481<li>It does not support folders as modules, directory indexes (e.g. 482<code>'./startup/index.js'</code>) must be fully specified.</li> 483<li>It does no extension searching. A file extension must be provided 484when the specifier is a relative or absolute file URL.</li> 485<li>It can load JSON modules, but an import assertion is required.</li> 486<li>It accepts only <code>.js</code>, <code>.mjs</code>, and <code>.cjs</code> extensions for JavaScript text 487files.</li> 488<li>It can be used to load JavaScript CommonJS modules. Such modules 489are passed through the <code>cjs-module-lexer</code> to try to identify named exports, 490which are available if they can be determined through static analysis. 491Imported CommonJS modules have their URLs converted to absolute 492paths and are then loaded via the CommonJS module loader.</li> 493</ul> 494<h4><code>package.json</code> and file extensions<span><a class="mark" href="#packagejson-and-file-extensions" id="packagejson-and-file-extensions">#</a></span><a aria-hidden="true" class="legacy" id="packages_package_json_and_file_extensions"></a></h4> 495<p>Within a package, the <a href="#nodejs-packagejson-field-definitions"><code>package.json</code></a> <a href="#type"><code>"type"</code></a> field defines how 496Node.js should interpret <code>.js</code> files. If a <code>package.json</code> file does not have a 497<code>"type"</code> field, <code>.js</code> files are treated as <a href="modules.html">CommonJS</a>.</p> 498<p>A <code>package.json</code> <code>"type"</code> value of <code>"module"</code> tells Node.js to interpret <code>.js</code> 499files within that package as using <a href="esm.html">ES module</a> syntax.</p> 500<p>The <code>"type"</code> field applies not only to initial entry points (<code>node my-app.js</code>) 501but also to files referenced by <code>import</code> statements and <code>import()</code> expressions.</p> 502<pre><code class="language-js"><span class="hljs-comment">// my-app.js, treated as an ES module because there is a package.json</span> 503<span class="hljs-comment">// file in the same folder with "type": "module".</span> 504 505<span class="hljs-keyword">import</span> <span class="hljs-string">'./startup/init.js'</span>; 506<span class="hljs-comment">// Loaded as ES module since ./startup contains no package.json file,</span> 507<span class="hljs-comment">// and therefore inherits the "type" value from one level up.</span> 508 509<span class="hljs-keyword">import</span> <span class="hljs-string">'commonjs-package'</span>; 510<span class="hljs-comment">// Loaded as CommonJS since ./node_modules/commonjs-package/package.json</span> 511<span class="hljs-comment">// lacks a "type" field or contains "type": "commonjs".</span> 512 513<span class="hljs-keyword">import</span> <span class="hljs-string">'./node_modules/commonjs-package/index.js'</span>; 514<span class="hljs-comment">// Loaded as CommonJS since ./node_modules/commonjs-package/package.json</span> 515<span class="hljs-comment">// lacks a "type" field or contains "type": "commonjs".</span></code> <button class="copy-button">copy</button></pre> 516<p>Files ending with <code>.mjs</code> are always loaded as <a href="esm.html">ES modules</a> regardless of 517the nearest parent <code>package.json</code>.</p> 518<p>Files ending with <code>.cjs</code> are always loaded as <a href="modules.html">CommonJS</a> regardless of the 519nearest parent <code>package.json</code>.</p> 520<pre><code class="language-js"><span class="hljs-keyword">import</span> <span class="hljs-string">'./legacy-file.cjs'</span>; 521<span class="hljs-comment">// Loaded as CommonJS since .cjs is always loaded as CommonJS.</span> 522 523<span class="hljs-keyword">import</span> <span class="hljs-string">'commonjs-package/src/index.mjs'</span>; 524<span class="hljs-comment">// Loaded as ES module since .mjs is always loaded as ES module.</span></code> <button class="copy-button">copy</button></pre> 525<p>The <code>.mjs</code> and <code>.cjs</code> extensions can be used to mix types within the same 526package:</p> 527<ul> 528<li> 529<p>Within a <code>"type": "module"</code> package, Node.js can be instructed to 530interpret a particular file as <a href="modules.html">CommonJS</a> by naming it with a <code>.cjs</code> 531extension (since both <code>.js</code> and <code>.mjs</code> files are treated as ES modules within 532a <code>"module"</code> package).</p> 533</li> 534<li> 535<p>Within a <code>"type": "commonjs"</code> package, Node.js can be instructed to 536interpret a particular file as an <a href="esm.html">ES module</a> by naming it with an <code>.mjs</code> 537extension (since both <code>.js</code> and <code>.cjs</code> files are treated as CommonJS within a 538<code>"commonjs"</code> package).</p> 539</li> 540</ul> 541<h4><code>--input-type</code> flag<span><a class="mark" href="#--input-type-flag" id="--input-type-flag">#</a></span><a aria-hidden="true" class="legacy" id="packages_input_type_flag"></a></h4> 542<div class="api_metadata"> 543<span>Added in: v12.0.0</span> 544</div> 545<p>Strings passed in as an argument to <code>--eval</code> (or <code>-e</code>), or piped to <code>node</code> via 546<code>STDIN</code>, are treated as <a href="esm.html">ES modules</a> when the <code>--input-type=module</code> flag 547is set.</p> 548<pre><code class="language-bash">node --input-type=module --<span class="hljs-built_in">eval</span> <span class="hljs-string">"import { sep } from 'node:path'; console.log(sep);"</span> 549 550<span class="hljs-built_in">echo</span> <span class="hljs-string">"import { sep } from 'node:path'; console.log(sep);"</span> | node --input-type=module</code> <button class="copy-button">copy</button></pre> 551<p>For completeness there is also <code>--input-type=commonjs</code>, for explicitly running 552string input as CommonJS. This is the default behavior if <code>--input-type</code> is 553unspecified.</p> 554</section><section><h3>Determining package manager<span><a class="mark" href="#determining-package-manager" id="determining-package-manager">#</a></span><a aria-hidden="true" class="legacy" id="packages_determining_package_manager"></a></h3> 555<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 556<p>While all Node.js projects are expected to be installable by all package 557managers once published, their development teams are often required to use one 558specific package manager. To make this process easier, Node.js ships with a 559tool called <a href="corepack.html">Corepack</a> that aims to make all package managers transparently 560available in your environment - provided you have Node.js installed.</p> 561<p>By default Corepack won't enforce any specific package manager and will use 562the generic "Last Known Good" versions associated with each Node.js release, 563but you can improve this experience by setting the <a href="#packagemanager"><code>"packageManager"</code></a> field 564in your project's <code>package.json</code>.</p> 565</section><section><h3>Package entry points<span><a class="mark" href="#package-entry-points" id="package-entry-points">#</a></span><a aria-hidden="true" class="legacy" id="packages_package_entry_points"></a></h3> 566<p>In a package's <code>package.json</code> file, two fields can define entry points for a 567package: <a href="#main"><code>"main"</code></a> and <a href="#exports"><code>"exports"</code></a>. Both fields apply to both ES module 568and CommonJS module entry points.</p> 569<p>The <a href="#main"><code>"main"</code></a> field is supported in all versions of Node.js, but its 570capabilities are limited: it only defines the main entry point of the package.</p> 571<p>The <a href="#exports"><code>"exports"</code></a> provides a modern alternative to <a href="#main"><code>"main"</code></a> allowing 572multiple entry points to be defined, conditional entry resolution support 573between environments, and <strong>preventing any other entry points besides those 574defined in <a href="#exports"><code>"exports"</code></a></strong>. This encapsulation allows module authors to 575clearly define the public interface for their package.</p> 576<p>For new packages targeting the currently supported versions of Node.js, the 577<a href="#exports"><code>"exports"</code></a> field is recommended. For packages supporting Node.js 10 and 578below, the <a href="#main"><code>"main"</code></a> field is required. If both <a href="#exports"><code>"exports"</code></a> and 579<a href="#main"><code>"main"</code></a> are defined, the <a href="#exports"><code>"exports"</code></a> field takes precedence over 580<a href="#main"><code>"main"</code></a> in supported versions of Node.js.</p> 581<p><a href="#conditional-exports">Conditional exports</a> can be used within <a href="#exports"><code>"exports"</code></a> to define different 582package entry points per environment, including whether the package is 583referenced via <code>require</code> or via <code>import</code>. For more information about supporting 584both CommonJS and ES modules in a single package please consult 585<a href="#dual-commonjses-module-packages">the dual CommonJS/ES module packages section</a>.</p> 586<p>Existing packages introducing the <a href="#exports"><code>"exports"</code></a> field will prevent consumers 587of the package from using any entry points that are not defined, including the 588<a href="#nodejs-packagejson-field-definitions"><code>package.json</code></a> (e.g. <code>require('your-package/package.json')</code>. <strong>This will 589likely be a breaking change.</strong></p> 590<p>To make the introduction of <a href="#exports"><code>"exports"</code></a> non-breaking, ensure that every 591previously supported entry point is exported. It is best to explicitly specify 592entry points so that the package's public API is well-defined. For example, 593a project that previously exported <code>main</code>, <code>lib</code>, 594<code>feature</code>, and the <code>package.json</code> could use the following <code>package.exports</code>:</p> 595<pre><code class="language-json"><span class="hljs-punctuation">{</span> 596 <span class="hljs-attr">"name"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"my-package"</span><span class="hljs-punctuation">,</span> 597 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 598 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/index.js"</span><span class="hljs-punctuation">,</span> 599 <span class="hljs-attr">"./lib"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/index.js"</span><span class="hljs-punctuation">,</span> 600 <span class="hljs-attr">"./lib/index"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/index.js"</span><span class="hljs-punctuation">,</span> 601 <span class="hljs-attr">"./lib/index.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/index.js"</span><span class="hljs-punctuation">,</span> 602 <span class="hljs-attr">"./feature"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature/index.js"</span><span class="hljs-punctuation">,</span> 603 <span class="hljs-attr">"./feature/index"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature/index.js"</span><span class="hljs-punctuation">,</span> 604 <span class="hljs-attr">"./feature/index.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature/index.js"</span><span class="hljs-punctuation">,</span> 605 <span class="hljs-attr">"./package.json"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./package.json"</span> 606 <span class="hljs-punctuation">}</span> 607<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 608<p>Alternatively a project could choose to export entire folders both with and 609without extensioned subpaths using export patterns:</p> 610<pre><code class="language-json"><span class="hljs-punctuation">{</span> 611 <span class="hljs-attr">"name"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"my-package"</span><span class="hljs-punctuation">,</span> 612 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 613 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/index.js"</span><span class="hljs-punctuation">,</span> 614 <span class="hljs-attr">"./lib"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/index.js"</span><span class="hljs-punctuation">,</span> 615 <span class="hljs-attr">"./lib/*"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/*.js"</span><span class="hljs-punctuation">,</span> 616 <span class="hljs-attr">"./lib/*.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/*.js"</span><span class="hljs-punctuation">,</span> 617 <span class="hljs-attr">"./feature"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature/index.js"</span><span class="hljs-punctuation">,</span> 618 <span class="hljs-attr">"./feature/*"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature/*.js"</span><span class="hljs-punctuation">,</span> 619 <span class="hljs-attr">"./feature/*.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature/*.js"</span><span class="hljs-punctuation">,</span> 620 <span class="hljs-attr">"./package.json"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./package.json"</span> 621 <span class="hljs-punctuation">}</span> 622<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 623<p>With the above providing backwards-compatibility for any minor package versions, 624a future major change for the package can then properly restrict the exports 625to only the specific feature exports exposed:</p> 626<pre><code class="language-json"><span class="hljs-punctuation">{</span> 627 <span class="hljs-attr">"name"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"my-package"</span><span class="hljs-punctuation">,</span> 628 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 629 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./lib/index.js"</span><span class="hljs-punctuation">,</span> 630 <span class="hljs-attr">"./feature/*.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature/*.js"</span><span class="hljs-punctuation">,</span> 631 <span class="hljs-attr">"./feature/internal/*"</span><span class="hljs-punctuation">:</span> <span class="hljs-literal"><span class="hljs-keyword">null</span></span> 632 <span class="hljs-punctuation">}</span> 633<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 634<h4>Main entry point export<span><a class="mark" href="#main-entry-point-export" id="main-entry-point-export">#</a></span><a aria-hidden="true" class="legacy" id="packages_main_entry_point_export"></a></h4> 635<p>When writing a new package, it is recommended to use the <a href="#exports"><code>"exports"</code></a> field:</p> 636<pre><code class="language-json"><span class="hljs-punctuation">{</span> 637 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span> 638<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 639<p>When the <a href="#exports"><code>"exports"</code></a> field is defined, all subpaths of the package are 640encapsulated and no longer available to importers. For example, 641<code>require('pkg/subpath.js')</code> throws an <a href="errors.html#err_package_path_not_exported"><code>ERR_PACKAGE_PATH_NOT_EXPORTED</code></a> 642error.</p> 643<p>This encapsulation of exports provides more reliable guarantees 644about package interfaces for tools and when handling semver upgrades for a 645package. It is not a strong encapsulation since a direct require of any 646absolute subpath of the package such as 647<code>require('/path/to/node_modules/pkg/subpath.js')</code> will still load <code>subpath.js</code>.</p> 648<p>All currently supported versions of Node.js and modern build tools support the 649<code>"exports"</code> field. For projects using an older version of Node.js or a related 650build tool, compatibility can be achieved by including the <code>"main"</code> field 651alongside <code>"exports"</code> pointing to the same module:</p> 652<pre><code class="language-json"><span class="hljs-punctuation">{</span> 653 <span class="hljs-attr">"main"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span><span class="hljs-punctuation">,</span> 654 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span> 655<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 656<h4>Subpath exports<span><a class="mark" href="#subpath-exports" id="subpath-exports">#</a></span><a aria-hidden="true" class="legacy" id="packages_subpath_exports"></a></h4> 657<div class="api_metadata"> 658<span>Added in: v12.7.0</span> 659</div> 660<p>When using the <a href="#exports"><code>"exports"</code></a> field, custom subpaths can be defined along 661with the main entry point by treating the main entry point as the 662<code>"."</code> subpath:</p> 663<pre><code class="language-json"><span class="hljs-punctuation">{</span> 664 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 665 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span><span class="hljs-punctuation">,</span> 666 <span class="hljs-attr">"./submodule.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./src/submodule.js"</span> 667 <span class="hljs-punctuation">}</span> 668<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 669<p>Now only the defined subpath in <a href="#exports"><code>"exports"</code></a> can be imported by a consumer:</p> 670<pre><code class="language-js"><span class="hljs-keyword">import</span> submodule <span class="hljs-keyword">from</span> <span class="hljs-string">'es-module-package/submodule.js'</span>; 671<span class="hljs-comment">// Loads ./node_modules/es-module-package/src/submodule.js</span></code> <button class="copy-button">copy</button></pre> 672<p>While other subpaths will error:</p> 673<pre><code class="language-js"><span class="hljs-keyword">import</span> submodule <span class="hljs-keyword">from</span> <span class="hljs-string">'es-module-package/private-module.js'</span>; 674<span class="hljs-comment">// Throws ERR_PACKAGE_PATH_NOT_EXPORTED</span></code> <button class="copy-button">copy</button></pre> 675<h5>Extensions in subpaths<span><a class="mark" href="#extensions-in-subpaths" id="extensions-in-subpaths">#</a></span><a aria-hidden="true" class="legacy" id="packages_extensions_in_subpaths"></a></h5> 676<p>Package authors should provide either extensioned (<code>import 'pkg/subpath.js'</code>) or 677extensionless (<code>import 'pkg/subpath'</code>) subpaths in their exports. This ensures 678that there is only one subpath for each exported module so that all dependents 679import the same consistent specifier, keeping the package contract clear for 680consumers and simplifying package subpath completions.</p> 681<p>Traditionally, packages tended to use the extensionless style, which has the 682benefits of readability and of masking the true path of the file within the 683package.</p> 684<p>With <a href="https://github.com/WICG/import-maps">import maps</a> now providing a standard for package resolution in browsers 685and other JavaScript runtimes, using the extensionless style can result in 686bloated import map definitions. Explicit file extensions can avoid this issue by 687enabling the import map to utilize a <a href="https://github.com/WICG/import-maps#packages-via-trailing-slashes">packages folder mapping</a> to map multiple 688subpaths where possible instead of a separate map entry per package subpath 689export. This also mirrors the requirement of using <a href="esm.html#mandatory-file-extensions">the full specifier path</a> 690in relative and absolute import specifiers.</p> 691<h4>Exports sugar<span><a class="mark" href="#exports-sugar" id="exports-sugar">#</a></span><a aria-hidden="true" class="legacy" id="packages_exports_sugar"></a></h4> 692<div class="api_metadata"> 693<span>Added in: v12.11.0</span> 694</div> 695<p>If the <code>"."</code> export is the only export, the <a href="#exports"><code>"exports"</code></a> field provides sugar 696for this case being the direct <a href="#exports"><code>"exports"</code></a> field value.</p> 697<pre><code class="language-json"><span class="hljs-punctuation">{</span> 698 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 699 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span> 700 <span class="hljs-punctuation">}</span> 701<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 702<p>can be written:</p> 703<pre><code class="language-json"><span class="hljs-punctuation">{</span> 704 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span> 705<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 706<h4>Subpath imports<span><a class="mark" href="#subpath-imports" id="subpath-imports">#</a></span><a aria-hidden="true" class="legacy" id="packages_subpath_imports"></a></h4> 707<div class="api_metadata"> 708<span>Added in: v14.6.0, v12.19.0</span> 709</div> 710<p>In addition to the <a href="#exports"><code>"exports"</code></a> field, there is a package <code>"imports"</code> field 711to create private mappings that only apply to import specifiers from within the 712package itself.</p> 713<p>Entries in the <code>"imports"</code> field must always start with <code>#</code> to ensure they are 714disambiguated from external package specifiers.</p> 715<p>For example, the imports field can be used to gain the benefits of conditional 716exports for internal modules:</p> 717<pre><code class="language-json"><span class="hljs-comment">// package.json</span> 718<span class="hljs-punctuation">{</span> 719 <span class="hljs-attr">"imports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 720 <span class="hljs-attr">"#dep"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 721 <span class="hljs-attr">"node"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"dep-node-native"</span><span class="hljs-punctuation">,</span> 722 <span class="hljs-attr">"default"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./dep-polyfill.js"</span> 723 <span class="hljs-punctuation">}</span> 724 <span class="hljs-punctuation">}</span><span class="hljs-punctuation">,</span> 725 <span class="hljs-attr">"dependencies"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 726 <span class="hljs-attr">"dep-node-native"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"^1.0.0"</span> 727 <span class="hljs-punctuation">}</span> 728<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 729<p>where <code>import '#dep'</code> does not get the resolution of the external package 730<code>dep-node-native</code> (including its exports in turn), and instead gets the local 731file <code>./dep-polyfill.js</code> relative to the package in other environments.</p> 732<p>Unlike the <code>"exports"</code> field, the <code>"imports"</code> field permits mapping to external 733packages.</p> 734<p>The resolution rules for the imports field are otherwise analogous to the 735exports field.</p> 736<h4>Subpath patterns<span><a class="mark" href="#subpath-patterns" id="subpath-patterns">#</a></span><a aria-hidden="true" class="legacy" id="packages_subpath_patterns"></a></h4> 737<div class="api_metadata"> 738<details class="changelog"><summary>History</summary> 739<table> 740<tbody><tr><th>Version</th><th>Changes</th></tr> 741<tr><td>v16.10.0, v14.19.0</td> 742<td><p>Support pattern trailers in "imports" field.</p></td></tr> 743<tr><td>v16.9.0, v14.19.0</td> 744<td><p>Support pattern trailers.</p></td></tr> 745<tr><td>v14.13.0, v12.20.0</td> 746<td><p><span>Added in: v14.13.0, v12.20.0</span></p></td></tr> 747</tbody></table> 748</details> 749</div> 750<p>For packages with a small number of exports or imports, we recommend 751explicitly listing each exports subpath entry. But for packages that have 752large numbers of subpaths, this might cause <code>package.json</code> bloat and 753maintenance issues.</p> 754<p>For these use cases, subpath export patterns can be used instead:</p> 755<pre><code class="language-json"><span class="hljs-comment">// ./node_modules/es-module-package/package.json</span> 756<span class="hljs-punctuation">{</span> 757 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 758 <span class="hljs-attr">"./features/*.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./src/features/*.js"</span> 759 <span class="hljs-punctuation">}</span><span class="hljs-punctuation">,</span> 760 <span class="hljs-attr">"imports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 761 <span class="hljs-attr">"#internal/*.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./src/internal/*.js"</span> 762 <span class="hljs-punctuation">}</span> 763<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 764<p><strong><code>*</code> maps expose nested subpaths as it is a string replacement syntax 765only.</strong></p> 766<p>All instances of <code>*</code> on the right hand side will then be replaced with this 767value, including if it contains any <code>/</code> separators.</p> 768<pre><code class="language-js"><span class="hljs-keyword">import</span> featureX <span class="hljs-keyword">from</span> <span class="hljs-string">'es-module-package/features/x.js'</span>; 769<span class="hljs-comment">// Loads ./node_modules/es-module-package/src/features/x.js</span> 770 771<span class="hljs-keyword">import</span> featureY <span class="hljs-keyword">from</span> <span class="hljs-string">'es-module-package/features/y/y.js'</span>; 772<span class="hljs-comment">// Loads ./node_modules/es-module-package/src/features/y/y.js</span> 773 774<span class="hljs-keyword">import</span> internalZ <span class="hljs-keyword">from</span> <span class="hljs-string">'#internal/z.js'</span>; 775<span class="hljs-comment">// Loads ./node_modules/es-module-package/src/internal/z.js</span></code> <button class="copy-button">copy</button></pre> 776<p>This is a direct static matching and replacement without any special handling 777for file extensions. Including the <code>"*.js"</code> on both sides of the mapping 778restricts the exposed package exports to only JS files.</p> 779<p>The property of exports being statically enumerable is maintained with exports 780patterns since the individual exports for a package can be determined by 781treating the right hand side target pattern as a <code>**</code> glob against the list of 782files within the package. Because <code>node_modules</code> paths are forbidden in exports 783targets, this expansion is dependent on only the files of the package itself.</p> 784<p>To exclude private subfolders from patterns, <code>null</code> targets can be used:</p> 785<pre><code class="language-json"><span class="hljs-comment">// ./node_modules/es-module-package/package.json</span> 786<span class="hljs-punctuation">{</span> 787 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 788 <span class="hljs-attr">"./features/*.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./src/features/*.js"</span><span class="hljs-punctuation">,</span> 789 <span class="hljs-attr">"./features/private-internal/*"</span><span class="hljs-punctuation">:</span> <span class="hljs-literal"><span class="hljs-keyword">null</span></span> 790 <span class="hljs-punctuation">}</span> 791<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 792<pre><code class="language-js"><span class="hljs-keyword">import</span> featureInternal <span class="hljs-keyword">from</span> <span class="hljs-string">'es-module-package/features/private-internal/m.js'</span>; 793<span class="hljs-comment">// Throws: ERR_PACKAGE_PATH_NOT_EXPORTED</span> 794 795<span class="hljs-keyword">import</span> featureX <span class="hljs-keyword">from</span> <span class="hljs-string">'es-module-package/features/x.js'</span>; 796<span class="hljs-comment">// Loads ./node_modules/es-module-package/src/features/x.js</span></code> <button class="copy-button">copy</button></pre> 797<h4>Conditional exports<span><a class="mark" href="#conditional-exports" id="conditional-exports">#</a></span><a aria-hidden="true" class="legacy" id="packages_conditional_exports"></a></h4> 798<div class="api_metadata"> 799<details class="changelog"><summary>History</summary> 800<table> 801<tbody><tr><th>Version</th><th>Changes</th></tr> 802<tr><td>v13.7.0, v12.16.0</td> 803<td><p>Unflag conditional exports.</p></td></tr> 804<tr><td>v13.2.0, v12.16.0</td> 805<td><p><span>Added in: v13.2.0, v12.16.0</span></p></td></tr> 806</tbody></table> 807</details> 808</div> 809<p>Conditional exports provide a way to map to different paths depending on 810certain conditions. They are supported for both CommonJS and ES module imports.</p> 811<p>For example, a package that wants to provide different ES module exports for 812<code>require()</code> and <code>import</code> can be written:</p> 813<pre><code class="language-json"><span class="hljs-comment">// package.json</span> 814<span class="hljs-punctuation">{</span> 815 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 816 <span class="hljs-attr">"import"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index-module.js"</span><span class="hljs-punctuation">,</span> 817 <span class="hljs-attr">"require"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index-require.cjs"</span> 818 <span class="hljs-punctuation">}</span><span class="hljs-punctuation">,</span> 819 <span class="hljs-attr">"type"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"module"</span> 820<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 821<p>Node.js implements the following conditions, listed in order from most 822specific to least specific as conditions should be defined:</p> 823<ul> 824<li><code>"node-addons"</code> - similar to <code>"node"</code> and matches for any Node.js environment. 825This condition can be used to provide an entry point which uses native C++ 826addons as opposed to an entry point which is more universal and doesn't rely 827on native addons. This condition can be disabled via the 828<a href="cli.html#--no-addons"><code>--no-addons</code> flag</a>.</li> 829<li><code>"node"</code> - matches for any Node.js environment. Can be a CommonJS or ES 830module file. <em>In most cases explicitly calling out the Node.js platform is 831not necessary.</em></li> 832<li><code>"import"</code> - matches when the package is loaded via <code>import</code> or 833<code>import()</code>, or via any top-level import or resolve operation by the 834ECMAScript module loader. Applies regardless of the module format of the 835target file. <em>Always mutually exclusive with <code>"require"</code>.</em></li> 836<li><code>"require"</code> - matches when the package is loaded via <code>require()</code>. The 837referenced file should be loadable with <code>require()</code> although the condition 838matches regardless of the module format of the target file. Expected 839formats include CommonJS, JSON, and native addons but not ES modules as 840<code>require()</code> doesn't support them. <em>Always mutually exclusive with 841<code>"import"</code>.</em></li> 842<li><code>"default"</code> - the generic fallback that always matches. Can be a CommonJS 843or ES module file. <em>This condition should always come last.</em></li> 844</ul> 845<p>Within the <a href="#exports"><code>"exports"</code></a> object, key order is significant. During condition 846matching, earlier entries have higher priority and take precedence over later 847entries. <em>The general rule is that conditions should be from most specific to 848least specific in object order</em>.</p> 849<p>Using the <code>"import"</code> and <code>"require"</code> conditions can lead to some hazards, 850which are further explained in <a href="#dual-commonjses-module-packages">the dual CommonJS/ES module packages section</a>.</p> 851<p>The <code>"node-addons"</code> condition can be used to provide an entry point which 852uses native C++ addons. However, this condition can be disabled via the 853<a href="cli.html#--no-addons"><code>--no-addons</code> flag</a>. When using <code>"node-addons"</code>, it's recommended to treat 854<code>"default"</code> as an enhancement that provides a more universal entry point, e.g. 855using WebAssembly instead of a native addon.</p> 856<p>Conditional exports can also be extended to exports subpaths, for example:</p> 857<pre><code class="language-json"><span class="hljs-punctuation">{</span> 858 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 859 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span><span class="hljs-punctuation">,</span> 860 <span class="hljs-attr">"./feature.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 861 <span class="hljs-attr">"node"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature-node.js"</span><span class="hljs-punctuation">,</span> 862 <span class="hljs-attr">"default"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature.js"</span> 863 <span class="hljs-punctuation">}</span> 864 <span class="hljs-punctuation">}</span> 865<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 866<p>Defines a package where <code>require('pkg/feature.js')</code> and 867<code>import 'pkg/feature.js'</code> could provide different implementations between 868Node.js and other JS environments.</p> 869<p>When using environment branches, always include a <code>"default"</code> condition where 870possible. Providing a <code>"default"</code> condition ensures that any unknown JS 871environments are able to use this universal implementation, which helps avoid 872these JS environments from having to pretend to be existing environments in 873order to support packages with conditional exports. For this reason, using 874<code>"node"</code> and <code>"default"</code> condition branches is usually preferable to using 875<code>"node"</code> and <code>"browser"</code> condition branches.</p> 876<h4>Nested conditions<span><a class="mark" href="#nested-conditions" id="nested-conditions">#</a></span><a aria-hidden="true" class="legacy" id="packages_nested_conditions"></a></h4> 877<p>In addition to direct mappings, Node.js also supports nested condition objects.</p> 878<p>For example, to define a package that only has dual mode entry points for 879use in Node.js but not the browser:</p> 880<pre><code class="language-json"><span class="hljs-punctuation">{</span> 881 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 882 <span class="hljs-attr">"node"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 883 <span class="hljs-attr">"import"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature-node.mjs"</span><span class="hljs-punctuation">,</span> 884 <span class="hljs-attr">"require"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature-node.cjs"</span> 885 <span class="hljs-punctuation">}</span><span class="hljs-punctuation">,</span> 886 <span class="hljs-attr">"default"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./feature.mjs"</span> 887 <span class="hljs-punctuation">}</span> 888<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 889<p>Conditions continue to be matched in order as with flat conditions. If 890a nested condition does not have any mapping it will continue checking 891the remaining conditions of the parent condition. In this way nested 892conditions behave analogously to nested JavaScript <code>if</code> statements.</p> 893<h4>Resolving user conditions<span><a class="mark" href="#resolving-user-conditions" id="resolving-user-conditions">#</a></span><a aria-hidden="true" class="legacy" id="packages_resolving_user_conditions"></a></h4> 894<div class="api_metadata"> 895<span>Added in: v14.9.0, v12.19.0</span> 896</div> 897<p>When running Node.js, custom user conditions can be added with the 898<code>--conditions</code> flag:</p> 899<pre><code class="language-bash">node --conditions=development index.js</code> <button class="copy-button">copy</button></pre> 900<p>which would then resolve the <code>"development"</code> condition in package imports and 901exports, while resolving the existing <code>"node"</code>, <code>"node-addons"</code>, <code>"default"</code>, 902<code>"import"</code>, and <code>"require"</code> conditions as appropriate.</p> 903<p>Any number of custom conditions can be set with repeat flags.</p> 904<h4>Community Conditions Definitions<span><a class="mark" href="#community-conditions-definitions" id="community-conditions-definitions">#</a></span><a aria-hidden="true" class="legacy" id="packages_community_conditions_definitions"></a></h4> 905<p>Condition strings other than the <code>"import"</code>, <code>"require"</code>, <code>"node"</code>, 906<code>"node-addons"</code> and <code>"default"</code> conditions 907<a href="#conditional-exports">implemented in Node.js core</a> are ignored by default.</p> 908<p>Other platforms may implement other conditions and user conditions can be 909enabled in Node.js via the <a href="#resolving-user-conditions"><code>--conditions</code> / <code>-C</code> flag</a>.</p> 910<p>Since custom package conditions require clear definitions to ensure correct 911usage, a list of common known package conditions and their strict definitions 912is provided below to assist with ecosystem coordination.</p> 913<ul> 914<li><code>"types"</code> - can be used by typing systems to resolve the typing file for 915the given export. <em>This condition should always be included first.</em></li> 916<li><code>"browser"</code> - any web browser environment.</li> 917<li><code>"development"</code> - can be used to define a development-only environment 918entry point, for example to provide additional debugging context such as 919better error messages when running in a development mode. <em>Must always be 920mutually exclusive with <code>"production"</code>.</em></li> 921<li><code>"production"</code> - can be used to define a production environment entry 922point. <em>Must always be mutually exclusive with <code>"development"</code>.</em></li> 923</ul> 924<p>For other runtimes, platform-specific condition key definitions are maintained 925by the <a href="https://wintercg.org/">WinterCG</a> in the <a href="https://runtime-keys.proposal.wintercg.org/">Runtime Keys</a> proposal specification.</p> 926<p>New conditions definitions may be added to this list by creating a pull request 927to the <a href="https://github.com/nodejs/node/blob/HEAD/doc/api/packages.md#conditions-definitions">Node.js documentation for this section</a>. The requirements for listing 928a new condition definition here are that:</p> 929<ul> 930<li>The definition should be clear and unambiguous for all implementers.</li> 931<li>The use case for why the condition is needed should be clearly justified.</li> 932<li>There should exist sufficient existing implementation usage.</li> 933<li>The condition name should not conflict with another condition definition or 934condition in wide usage.</li> 935<li>The listing of the condition definition should provide a coordination 936benefit to the ecosystem that wouldn't otherwise be possible. For example, 937this would not necessarily be the case for company-specific or 938application-specific conditions.</li> 939<li>The condition should be such that a Node.js user would expect it to be in 940Node.js core documentation. The <code>"types"</code> condition is a good example: It 941doesn't really belong in the <a href="https://runtime-keys.proposal.wintercg.org/">Runtime Keys</a> proposal but is a good fit 942here in the Node.js docs.</li> 943</ul> 944<p>The above definitions may be moved to a dedicated conditions registry in due 945course.</p> 946<h4>Self-referencing a package using its name<span><a class="mark" href="#self-referencing-a-package-using-its-name" id="self-referencing-a-package-using-its-name">#</a></span><a aria-hidden="true" class="legacy" id="packages_self_referencing_a_package_using_its_name"></a></h4> 947<div class="api_metadata"> 948<details class="changelog"><summary>History</summary> 949<table> 950<tbody><tr><th>Version</th><th>Changes</th></tr> 951<tr><td>v13.6.0, v12.16.0</td> 952<td><p>Unflag self-referencing a package using its name.</p></td></tr> 953<tr><td>v13.1.0, v12.16.0</td> 954<td><p><span>Added in: v13.1.0, v12.16.0</span></p></td></tr> 955</tbody></table> 956</details> 957</div> 958<p>Within a package, the values defined in the package's 959<code>package.json</code> <a href="#exports"><code>"exports"</code></a> field can be referenced via the package's name. 960For example, assuming the <code>package.json</code> is:</p> 961<pre><code class="language-json"><span class="hljs-comment">// package.json</span> 962<span class="hljs-punctuation">{</span> 963 <span class="hljs-attr">"name"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"a-package"</span><span class="hljs-punctuation">,</span> 964 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 965 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.mjs"</span><span class="hljs-punctuation">,</span> 966 <span class="hljs-attr">"./foo.js"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./foo.js"</span> 967 <span class="hljs-punctuation">}</span> 968<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 969<p>Then any module <em>in that package</em> can reference an export in the package itself:</p> 970<pre><code class="language-js"><span class="hljs-comment">// ./a-module.mjs</span> 971<span class="hljs-keyword">import</span> { something } <span class="hljs-keyword">from</span> <span class="hljs-string">'a-package'</span>; <span class="hljs-comment">// Imports "something" from ./index.mjs.</span></code> <button class="copy-button">copy</button></pre> 972<p>Self-referencing is available only if <code>package.json</code> has <a href="#exports"><code>"exports"</code></a>, and 973will allow importing only what that <a href="#exports"><code>"exports"</code></a> (in the <code>package.json</code>) 974allows. So the code below, given the previous package, will generate a runtime 975error:</p> 976<pre><code class="language-js"><span class="hljs-comment">// ./another-module.mjs</span> 977 978<span class="hljs-comment">// Imports "another" from ./m.mjs. Fails because</span> 979<span class="hljs-comment">// the "package.json" "exports" field</span> 980<span class="hljs-comment">// does not provide an export named "./m.mjs".</span> 981<span class="hljs-keyword">import</span> { another } <span class="hljs-keyword">from</span> <span class="hljs-string">'a-package/m.mjs'</span>;</code> <button class="copy-button">copy</button></pre> 982<p>Self-referencing is also available when using <code>require</code>, both in an ES module, 983and in a CommonJS one. For example, this code will also work:</p> 984<pre><code class="language-js cjs"><span class="hljs-comment">// ./a-module.js</span> 985<span class="hljs-keyword">const</span> { something } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'a-package/foo.js'</span>); <span class="hljs-comment">// Loads from ./foo.js.</span></code> <button class="copy-button">copy</button></pre> 986<p>Finally, self-referencing also works with scoped packages. For example, this 987code will also work:</p> 988<pre><code class="language-json"><span class="hljs-comment">// package.json</span> 989<span class="hljs-punctuation">{</span> 990 <span class="hljs-attr">"name"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"@my/package"</span><span class="hljs-punctuation">,</span> 991 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span> 992<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 993<pre><code class="language-js cjs"><span class="hljs-comment">// ./index.js</span> 994<span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span> = <span class="hljs-number">42</span>;</code> <button class="copy-button">copy</button></pre> 995<pre><code class="language-js cjs"><span class="hljs-comment">// ./other.js</span> 996<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-built_in">require</span>(<span class="hljs-string">'@my/package'</span>));</code> <button class="copy-button">copy</button></pre> 997<pre><code class="language-console"><span class="hljs-meta prompt_">$ </span><span class="language-bash">node other.js</span> 99842</code> <button class="copy-button">copy</button></pre> 999</section><section><h3>Dual CommonJS/ES module packages<span><a class="mark" href="#dual-commonjses-module-packages" id="dual-commonjses-module-packages">#</a></span><a aria-hidden="true" class="legacy" id="packages_dual_commonjs_es_module_packages"></a></h3> 1000<p>Prior to the introduction of support for ES modules in Node.js, it was a common 1001pattern for package authors to include both CommonJS and ES module JavaScript 1002sources in their package, with <code>package.json</code> <a href="#main"><code>"main"</code></a> specifying the 1003CommonJS entry point and <code>package.json</code> <code>"module"</code> specifying the ES module 1004entry point. 1005This enabled Node.js to run the CommonJS entry point while build tools such as 1006bundlers used the ES module entry point, since Node.js ignored (and still 1007ignores) the top-level <code>"module"</code> field.</p> 1008<p>Node.js can now run ES module entry points, and a package can contain both 1009CommonJS and ES module entry points (either via separate specifiers such as 1010<code>'pkg'</code> and <code>'pkg/es-module'</code>, or both at the same specifier via <a href="#conditional-exports">Conditional 1011exports</a>). Unlike in the scenario where <code>"module"</code> is only used by bundlers, 1012or ES module files are transpiled into CommonJS on the fly before evaluation by 1013Node.js, the files referenced by the ES module entry point are evaluated as ES 1014modules.</p> 1015<h4>Dual package hazard<span><a class="mark" href="#dual-package-hazard" id="dual-package-hazard">#</a></span><a aria-hidden="true" class="legacy" id="packages_dual_package_hazard"></a></h4> 1016<p>When an application is using a package that provides both CommonJS and ES module 1017sources, there is a risk of certain bugs if both versions of the package get 1018loaded. This potential comes from the fact that the <code>pkgInstance</code> created by 1019<code>const pkgInstance = require('pkg')</code> is not the same as the <code>pkgInstance</code> 1020created by <code>import pkgInstance from 'pkg'</code> (or an alternative main path like 1021<code>'pkg/module'</code>). This is the “dual package hazard,” where two versions of the 1022same package can be loaded within the same runtime environment. While it is 1023unlikely that an application or package would intentionally load both versions 1024directly, it is common for an application to load one version while a dependency 1025of the application loads the other version. This hazard can happen because 1026Node.js supports intermixing CommonJS and ES modules, and can lead to unexpected 1027behavior.</p> 1028<p>If the package main export is a constructor, an <code>instanceof</code> comparison of 1029instances created by the two versions returns <code>false</code>, and if the export is an 1030object, properties added to one (like <code>pkgInstance.foo = 3</code>) are not present on 1031the other. This differs from how <code>import</code> and <code>require</code> statements work in 1032all-CommonJS or all-ES module environments, respectively, and therefore is 1033surprising to users. It also differs from the behavior users are familiar with 1034when using transpilation via tools like <a href="https://babeljs.io/">Babel</a> or <a href="https://github.com/standard-things/esm#readme"><code>esm</code></a>.</p> 1035<h4>Writing dual packages while avoiding or minimizing hazards<span><a class="mark" href="#writing-dual-packages-while-avoiding-or-minimizing-hazards" id="writing-dual-packages-while-avoiding-or-minimizing-hazards">#</a></span><a aria-hidden="true" class="legacy" id="packages_writing_dual_packages_while_avoiding_or_minimizing_hazards"></a></h4> 1036<p>First, the hazard described in the previous section occurs when a package 1037contains both CommonJS and ES module sources and both sources are provided for 1038use in Node.js, either via separate main entry points or exported paths. A 1039package might instead be written where any version of Node.js receives only 1040CommonJS sources, and any separate ES module sources the package might contain 1041are intended only for other environments such as browsers. Such a package 1042would be usable by any version of Node.js, since <code>import</code> can refer to CommonJS 1043files; but it would not provide any of the advantages of using ES module syntax.</p> 1044<p>A package might also switch from CommonJS to ES module syntax in a <a href="https://semver.org/">breaking 1045change</a> version bump. This has the disadvantage that the 1046newest version of the package would only be usable in ES module-supporting 1047versions of Node.js.</p> 1048<p>Every pattern has tradeoffs, but there are two broad approaches that satisfy the 1049following conditions:</p> 1050<ol> 1051<li>The package is usable via both <code>require</code> and <code>import</code>.</li> 1052<li>The package is usable in both current Node.js and older versions of Node.js 1053that lack support for ES modules.</li> 1054<li>The package main entry point, e.g. <code>'pkg'</code> can be used by both <code>require</code> to 1055resolve to a CommonJS file and by <code>import</code> to resolve to an ES module file. 1056(And likewise for exported paths, e.g. <code>'pkg/feature'</code>.)</li> 1057<li>The package provides named exports, e.g. <code>import { name } from 'pkg'</code> rather 1058than <code>import pkg from 'pkg'; pkg.name</code>.</li> 1059<li>The package is potentially usable in other ES module environments such as 1060browsers.</li> 1061<li>The hazards described in the previous section are avoided or minimized.</li> 1062</ol> 1063<h5>Approach #1: Use an ES module wrapper<span><a class="mark" href="#approach-1-use-an-es-module-wrapper" id="approach-1-use-an-es-module-wrapper">#</a></span><a aria-hidden="true" class="legacy" id="packages_approach_1_use_an_es_module_wrapper"></a></h5> 1064<p>Write the package in CommonJS or transpile ES module sources into CommonJS, and 1065create an ES module wrapper file that defines the named exports. Using 1066<a href="#conditional-exports">Conditional exports</a>, the ES module wrapper is used for <code>import</code> and the 1067CommonJS entry point for <code>require</code>.</p> 1068<pre><code class="language-json"><span class="hljs-comment">// ./node_modules/pkg/package.json</span> 1069<span class="hljs-punctuation">{</span> 1070 <span class="hljs-attr">"type"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"module"</span><span class="hljs-punctuation">,</span> 1071 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 1072 <span class="hljs-attr">"import"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./wrapper.mjs"</span><span class="hljs-punctuation">,</span> 1073 <span class="hljs-attr">"require"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.cjs"</span> 1074 <span class="hljs-punctuation">}</span> 1075<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1076<p>The preceding example uses explicit extensions <code>.mjs</code> and <code>.cjs</code>. 1077If your files use the <code>.js</code> extension, <code>"type": "module"</code> will cause such files 1078to be treated as ES modules, just as <code>"type": "commonjs"</code> would cause them 1079to be treated as CommonJS. 1080See <a href="esm.html#enabling">Enabling</a>.</p> 1081<pre><code class="language-js cjs"><span class="hljs-comment">// ./node_modules/pkg/index.cjs</span> 1082<span class="hljs-built_in">exports</span>.<span class="hljs-property">name</span> = <span class="hljs-string">'value'</span>;</code> <button class="copy-button">copy</button></pre> 1083<pre><code class="language-js"><span class="hljs-comment">// ./node_modules/pkg/wrapper.mjs</span> 1084<span class="hljs-keyword">import</span> cjsModule <span class="hljs-keyword">from</span> <span class="hljs-string">'./index.cjs'</span>; 1085<span class="hljs-keyword">export</span> <span class="hljs-keyword">const</span> name = cjsModule.<span class="hljs-property">name</span>;</code> <button class="copy-button">copy</button></pre> 1086<p>In this example, the <code>name</code> from <code>import { name } from 'pkg'</code> is the same 1087singleton as the <code>name</code> from <code>const { name } = require('pkg')</code>. Therefore <code>===</code> 1088returns <code>true</code> when comparing the two <code>name</code>s and the divergent specifier hazard 1089is avoided.</p> 1090<p>If the module is not simply a list of named exports, but rather contains a 1091unique function or object export like <code>module.exports = function () { ... }</code>, 1092or if support in the wrapper for the <code>import pkg from 'pkg'</code> pattern is desired, 1093then the wrapper would instead be written to export the default optionally 1094along with any named exports as well:</p> 1095<pre><code class="language-js"><span class="hljs-keyword">import</span> cjsModule <span class="hljs-keyword">from</span> <span class="hljs-string">'./index.cjs'</span>; 1096<span class="hljs-keyword">export</span> <span class="hljs-keyword">const</span> name = cjsModule.<span class="hljs-property">name</span>; 1097<span class="hljs-keyword">export</span> <span class="hljs-keyword">default</span> cjsModule;</code> <button class="copy-button">copy</button></pre> 1098<p>This approach is appropriate for any of the following use cases:</p> 1099<ul> 1100<li>The package is currently written in CommonJS and the author would prefer not 1101to refactor it into ES module syntax, but wishes to provide named exports for 1102ES module consumers.</li> 1103<li>The package has other packages that depend on it, and the end user might 1104install both this package and those other packages. For example a <code>utilities</code> 1105package is used directly in an application, and a <code>utilities-plus</code> package 1106adds a few more functions to <code>utilities</code>. Because the wrapper exports 1107underlying CommonJS files, it doesn't matter if <code>utilities-plus</code> is written in 1108CommonJS or ES module syntax; it will work either way.</li> 1109<li>The package stores internal state, and the package author would prefer not to 1110refactor the package to isolate its state management. See the next section.</li> 1111</ul> 1112<p>A variant of this approach not requiring conditional exports for consumers could 1113be to add an export, e.g. <code>"./module"</code>, to point to an all-ES module-syntax 1114version of the package. This could be used via <code>import 'pkg/module'</code> by users 1115who are certain that the CommonJS version will not be loaded anywhere in the 1116application, such as by dependencies; or if the CommonJS version can be loaded 1117but doesn't affect the ES module version (for example, because the package is 1118stateless):</p> 1119<pre><code class="language-json"><span class="hljs-comment">// ./node_modules/pkg/package.json</span> 1120<span class="hljs-punctuation">{</span> 1121 <span class="hljs-attr">"type"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"module"</span><span class="hljs-punctuation">,</span> 1122 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 1123 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.cjs"</span><span class="hljs-punctuation">,</span> 1124 <span class="hljs-attr">"./module"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./wrapper.mjs"</span> 1125 <span class="hljs-punctuation">}</span> 1126<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1127<h5>Approach #2: Isolate state<span><a class="mark" href="#approach-2-isolate-state" id="approach-2-isolate-state">#</a></span><a aria-hidden="true" class="legacy" id="packages_approach_2_isolate_state"></a></h5> 1128<p>A <a href="#nodejs-packagejson-field-definitions"><code>package.json</code></a> file can define the separate CommonJS and ES module entry 1129points directly:</p> 1130<pre><code class="language-json"><span class="hljs-comment">// ./node_modules/pkg/package.json</span> 1131<span class="hljs-punctuation">{</span> 1132 <span class="hljs-attr">"type"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"module"</span><span class="hljs-punctuation">,</span> 1133 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 1134 <span class="hljs-attr">"import"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.mjs"</span><span class="hljs-punctuation">,</span> 1135 <span class="hljs-attr">"require"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.cjs"</span> 1136 <span class="hljs-punctuation">}</span> 1137<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1138<p>This can be done if both the CommonJS and ES module versions of the package are 1139equivalent, for example because one is the transpiled output of the other; and 1140the package's management of state is carefully isolated (or the package is 1141stateless).</p> 1142<p>The reason that state is an issue is because both the CommonJS and ES module 1143versions of the package might get used within an application; for example, the 1144user's application code could <code>import</code> the ES module version while a dependency 1145<code>require</code>s the CommonJS version. If that were to occur, two copies of the 1146package would be loaded in memory and therefore two separate states would be 1147present. This would likely cause hard-to-troubleshoot bugs.</p> 1148<p>Aside from writing a stateless package (if JavaScript's <code>Math</code> were a package, 1149for example, it would be stateless as all of its methods are static), there are 1150some ways to isolate state so that it's shared between the potentially loaded 1151CommonJS and ES module instances of the package:</p> 1152<ol> 1153<li> 1154<p>If possible, contain all state within an instantiated object. JavaScript's 1155<code>Date</code>, for example, needs to be instantiated to contain state; if it were a 1156package, it would be used like this:</p> 1157<pre><code class="language-js"><span class="hljs-keyword">import</span> <span class="hljs-title class_">Date</span> <span class="hljs-keyword">from</span> <span class="hljs-string">'date'</span>; 1158<span class="hljs-keyword">const</span> someDate = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Date</span>(); 1159<span class="hljs-comment">// someDate contains state; Date does not</span></code> <button class="copy-button">copy</button></pre> 1160<p>The <code>new</code> keyword isn't required; a package's function can return a new 1161object, or modify a passed-in object, to keep the state external to the 1162package.</p> 1163</li> 1164<li> 1165<p>Isolate the state in one or more CommonJS files that are shared between the 1166CommonJS and ES module versions of the package. For example, if the CommonJS 1167and ES module entry points are <code>index.cjs</code> and <code>index.mjs</code>, respectively:</p> 1168<pre><code class="language-js cjs"><span class="hljs-comment">// ./node_modules/pkg/index.cjs</span> 1169<span class="hljs-keyword">const</span> state = <span class="hljs-built_in">require</span>(<span class="hljs-string">'./state.cjs'</span>); 1170<span class="hljs-variable language_">module</span>.<span class="hljs-property">exports</span>.<span class="hljs-property">state</span> = state;</code> <button class="copy-button">copy</button></pre> 1171<pre><code class="language-js"><span class="hljs-comment">// ./node_modules/pkg/index.mjs</span> 1172<span class="hljs-keyword">import</span> state <span class="hljs-keyword">from</span> <span class="hljs-string">'./state.cjs'</span>; 1173<span class="hljs-keyword">export</span> { 1174 state, 1175};</code> <button class="copy-button">copy</button></pre> 1176<p>Even if <code>pkg</code> is used via both <code>require</code> and <code>import</code> in an application (for 1177example, via <code>import</code> in application code and via <code>require</code> by a dependency) 1178each reference of <code>pkg</code> will contain the same state; and modifying that 1179state from either module system will apply to both.</p> 1180</li> 1181</ol> 1182<p>Any plugins that attach to the package's singleton would need to separately 1183attach to both the CommonJS and ES module singletons.</p> 1184<p>This approach is appropriate for any of the following use cases:</p> 1185<ul> 1186<li>The package is currently written in ES module syntax and the package author 1187wants that version to be used wherever such syntax is supported.</li> 1188<li>The package is stateless or its state can be isolated without too much 1189difficulty.</li> 1190<li>The package is unlikely to have other public packages that depend on it, or if 1191it does, the package is stateless or has state that need not be shared between 1192dependencies or with the overall application.</li> 1193</ul> 1194<p>Even with isolated state, there is still the cost of possible extra code 1195execution between the CommonJS and ES module versions of a package.</p> 1196<p>As with the previous approach, a variant of this approach not requiring 1197conditional exports for consumers could be to add an export, e.g. 1198<code>"./module"</code>, to point to an all-ES module-syntax version of the package:</p> 1199<pre><code class="language-json"><span class="hljs-comment">// ./node_modules/pkg/package.json</span> 1200<span class="hljs-punctuation">{</span> 1201 <span class="hljs-attr">"type"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"module"</span><span class="hljs-punctuation">,</span> 1202 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 1203 <span class="hljs-attr">"."</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.cjs"</span><span class="hljs-punctuation">,</span> 1204 <span class="hljs-attr">"./module"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.mjs"</span> 1205 <span class="hljs-punctuation">}</span> 1206<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1207</section><section><h3>Node.js <code>package.json</code> field definitions<span><a class="mark" href="#nodejs-packagejson-field-definitions" id="nodejs-packagejson-field-definitions">#</a></span><a aria-hidden="true" class="legacy" id="packages_node_js_package_json_field_definitions"></a></h3> 1208<p>This section describes the fields used by the Node.js runtime. Other tools (such 1209as <a href="https://docs.npmjs.com/cli/v8/configuring-npm/package-json">npm</a>) use 1210additional fields which are ignored by Node.js and not documented here.</p> 1211<p>The following fields in <code>package.json</code> files are used in Node.js:</p> 1212<ul> 1213<li><a href="#name"><code>"name"</code></a> - Relevant when using named imports within a package. Also used 1214by package managers as the name of the package.</li> 1215<li><a href="#main"><code>"main"</code></a> - The default module when loading the package, if exports is not 1216specified, and in versions of Node.js prior to the introduction of exports.</li> 1217<li><a href="#packagemanager"><code>"packageManager"</code></a> - The package manager recommended when contributing to 1218the package. Leveraged by the <a href="corepack.html">Corepack</a> shims.</li> 1219<li><a href="#type"><code>"type"</code></a> - The package type determining whether to load <code>.js</code> files as 1220CommonJS or ES modules.</li> 1221<li><a href="#exports"><code>"exports"</code></a> - Package exports and conditional exports. When present, 1222limits which submodules can be loaded from within the package.</li> 1223<li><a href="#imports"><code>"imports"</code></a> - Package imports, for use by modules within the package 1224itself.</li> 1225</ul> 1226<h4><code>"name"</code><span><a class="mark" href="#name" id="name">#</a></span><a aria-hidden="true" class="legacy" id="packages_name"></a></h4> 1227<div class="api_metadata"> 1228<details class="changelog"><summary>History</summary> 1229<table> 1230<tbody><tr><th>Version</th><th>Changes</th></tr> 1231<tr><td>v13.6.0, v12.16.0</td> 1232<td><p>Remove the <code>--experimental-resolve-self</code> option.</p></td></tr> 1233<tr><td>v13.1.0, v12.16.0</td> 1234<td><p><span>Added in: v13.1.0, v12.16.0</span></p></td></tr> 1235</tbody></table> 1236</details> 1237</div> 1238<ul> 1239<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1240</ul> 1241<pre><code class="language-json"><span class="hljs-punctuation">{</span> 1242 <span class="hljs-attr">"name"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"package-name"</span> 1243<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1244<p>The <code>"name"</code> field defines your package's name. Publishing to the 1245<em>npm</em> registry requires a name that satisfies 1246<a href="https://docs.npmjs.com/files/package.json#name">certain requirements</a>.</p> 1247<p>The <code>"name"</code> field can be used in addition to the <a href="#exports"><code>"exports"</code></a> field to 1248<a href="#self-referencing-a-package-using-its-name">self-reference</a> a package using its name.</p> 1249<h4><code>"main"</code><span><a class="mark" href="#main" id="main">#</a></span><a aria-hidden="true" class="legacy" id="packages_main"></a></h4> 1250<div class="api_metadata"> 1251<span>Added in: v0.4.0</span> 1252</div> 1253<ul> 1254<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1255</ul> 1256<pre><code class="language-json"><span class="hljs-punctuation">{</span> 1257 <span class="hljs-attr">"main"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span> 1258<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1259<p>The <code>"main"</code> field defines the entry point of a package when imported by name 1260via a <code>node_modules</code> lookup. Its value is a path.</p> 1261<p>When a package has an <a href="#exports"><code>"exports"</code></a> field, this will take precedence over the 1262<code>"main"</code> field when importing the package by name.</p> 1263<p>It also defines the script that is used when the <a href="modules.html#folders-as-modules">package directory is loaded 1264via <code>require()</code></a>.</p> 1265<pre><code class="language-js cjs"><span class="hljs-comment">// This resolves to ./path/to/directory/index.js.</span> 1266<span class="hljs-built_in">require</span>(<span class="hljs-string">'./path/to/directory'</span>);</code> <button class="copy-button">copy</button></pre> 1267<h4><code>"packageManager"</code><span><a class="mark" href="#packagemanager" id="packagemanager">#</a></span><a aria-hidden="true" class="legacy" id="packages_packagemanager"></a></h4> 1268<div class="api_metadata"> 1269<span>Added in: v16.9.0, v14.19.0</span> 1270</div> 1271<p></p><div class="api_stability api_stability_1"><a href="documentation.html#stability-index">Stability: 1</a> - Experimental</div><p></p> 1272<ul> 1273<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1274</ul> 1275<pre><code class="language-json"><span class="hljs-punctuation">{</span> 1276 <span class="hljs-attr">"packageManager"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"<package manager name>@<version>"</span> 1277<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1278<p>The <code>"packageManager"</code> field defines which package manager is expected to be 1279used when working on the current project. It can be set to any of the 1280<a href="corepack.html#supported-package-managers">supported package managers</a>, and will ensure that your teams use the exact 1281same package manager versions without having to install anything else other than 1282Node.js.</p> 1283<p>This field is currently experimental and needs to be opted-in; check the 1284<a href="corepack.html">Corepack</a> page for details about the procedure.</p> 1285<h4><code>"type"</code><span><a class="mark" href="#type" id="type">#</a></span><a aria-hidden="true" class="legacy" id="packages_type"></a></h4> 1286<div class="api_metadata"> 1287<details class="changelog"><summary>History</summary> 1288<table> 1289<tbody><tr><th>Version</th><th>Changes</th></tr> 1290<tr><td>v13.2.0, v12.17.0</td> 1291<td><p>Unflag <code>--experimental-modules</code>.</p></td></tr> 1292<tr><td>v12.0.0</td> 1293<td><p><span>Added in: v12.0.0</span></p></td></tr> 1294</tbody></table> 1295</details> 1296</div> 1297<ul> 1298<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1299</ul> 1300<p>The <code>"type"</code> field defines the module format that Node.js uses for all 1301<code>.js</code> files that have that <code>package.json</code> file as their nearest parent.</p> 1302<p>Files ending with <code>.js</code> are loaded as ES modules when the nearest parent 1303<code>package.json</code> file contains a top-level field <code>"type"</code> with a value of 1304<code>"module"</code>.</p> 1305<p>The nearest parent <code>package.json</code> is defined as the first <code>package.json</code> found 1306when searching in the current folder, that folder's parent, and so on up 1307until a node_modules folder or the volume root is reached.</p> 1308<pre><code class="language-json"><span class="hljs-comment">// package.json</span> 1309<span class="hljs-punctuation">{</span> 1310 <span class="hljs-attr">"type"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"module"</span> 1311<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1312<pre><code class="language-bash"><span class="hljs-comment"># In same folder as preceding package.json</span> 1313node my-app.js <span class="hljs-comment"># Runs as ES module</span></code> <button class="copy-button">copy</button></pre> 1314<p>If the nearest parent <code>package.json</code> lacks a <code>"type"</code> field, or contains 1315<code>"type": "commonjs"</code>, <code>.js</code> files are treated as <a href="modules.html">CommonJS</a>. If the volume 1316root is reached and no <code>package.json</code> is found, <code>.js</code> files are treated as 1317<a href="modules.html">CommonJS</a>.</p> 1318<p><code>import</code> statements of <code>.js</code> files are treated as ES modules if the nearest 1319parent <code>package.json</code> contains <code>"type": "module"</code>.</p> 1320<pre><code class="language-js"><span class="hljs-comment">// my-app.js, part of the same example as above</span> 1321<span class="hljs-keyword">import</span> <span class="hljs-string">'./startup.js'</span>; <span class="hljs-comment">// Loaded as ES module because of package.json</span></code> <button class="copy-button">copy</button></pre> 1322<p>Regardless of the value of the <code>"type"</code> field, <code>.mjs</code> files are always treated 1323as ES modules and <code>.cjs</code> files are always treated as CommonJS.</p> 1324<h4><code>"exports"</code><span><a class="mark" href="#exports" id="exports">#</a></span><a aria-hidden="true" class="legacy" id="packages_exports"></a></h4> 1325<div class="api_metadata"> 1326<details class="changelog"><summary>History</summary> 1327<table> 1328<tbody><tr><th>Version</th><th>Changes</th></tr> 1329<tr><td>v14.13.0, v12.20.0</td> 1330<td><p>Add support for <code>"exports"</code> patterns.</p></td></tr> 1331<tr><td>v13.7.0, v12.17.0</td> 1332<td><p>Unflag conditional exports.</p></td></tr> 1333<tr><td>v13.7.0, v12.16.0</td> 1334<td><p>Implement logical conditional exports ordering.</p></td></tr> 1335<tr><td>v13.7.0, v12.16.0</td> 1336<td><p>Remove the <code>--experimental-conditional-exports</code> option. In 12.16.0, conditional exports are still behind <code>--experimental-modules</code>.</p></td></tr> 1337<tr><td>v13.2.0, v12.16.0</td> 1338<td><p>Implement conditional exports.</p></td></tr> 1339<tr><td>v12.7.0</td> 1340<td><p><span>Added in: v12.7.0</span></p></td></tr> 1341</tbody></table> 1342</details> 1343</div> 1344<ul> 1345<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1346</ul> 1347<pre><code class="language-json"><span class="hljs-punctuation">{</span> 1348 <span class="hljs-attr">"exports"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./index.js"</span> 1349<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1350<p>The <code>"exports"</code> field allows defining the <a href="#package-entry-points">entry points</a> of a package when 1351imported by name loaded either via a <code>node_modules</code> lookup or a 1352<a href="#self-referencing-a-package-using-its-name">self-reference</a> to its own name. It is supported in Node.js 12+ as an 1353alternative to the <a href="#main"><code>"main"</code></a> that can support defining <a href="#subpath-exports">subpath exports</a> 1354and <a href="#conditional-exports">conditional exports</a> while encapsulating internal unexported modules.</p> 1355<p><a href="#conditional-exports">Conditional Exports</a> can also be used within <code>"exports"</code> to define different 1356package entry points per environment, including whether the package is 1357referenced via <code>require</code> or via <code>import</code>.</p> 1358<p>All paths defined in the <code>"exports"</code> must be relative file URLs starting with 1359<code>./</code>.</p> 1360<h4><code>"imports"</code><span><a class="mark" href="#imports" id="imports">#</a></span><a aria-hidden="true" class="legacy" id="packages_imports"></a></h4> 1361<div class="api_metadata"> 1362<span>Added in: v14.6.0, v12.19.0</span> 1363</div> 1364<ul> 1365<li>Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 1366</ul> 1367<pre><code class="language-json"><span class="hljs-comment">// package.json</span> 1368<span class="hljs-punctuation">{</span> 1369 <span class="hljs-attr">"imports"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 1370 <span class="hljs-attr">"#dep"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 1371 <span class="hljs-attr">"node"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"dep-node-native"</span><span class="hljs-punctuation">,</span> 1372 <span class="hljs-attr">"default"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"./dep-polyfill.js"</span> 1373 <span class="hljs-punctuation">}</span> 1374 <span class="hljs-punctuation">}</span><span class="hljs-punctuation">,</span> 1375 <span class="hljs-attr">"dependencies"</span><span class="hljs-punctuation">:</span> <span class="hljs-punctuation">{</span> 1376 <span class="hljs-attr">"dep-node-native"</span><span class="hljs-punctuation">:</span> <span class="hljs-string">"^1.0.0"</span> 1377 <span class="hljs-punctuation">}</span> 1378<span class="hljs-punctuation">}</span></code> <button class="copy-button">copy</button></pre> 1379<p>Entries in the imports field must be strings starting with <code>#</code>.</p> 1380<p>Package imports permit mapping to external packages.</p> 1381<p>This field defines <a href="#subpath-imports">subpath imports</a> for the current package.</p></section> 1382 <!-- API END --> 1383 </div> 1384 </div> 1385 </div> 1386</body> 1387</html> 1388