13af6ab5fSopenharmony_ci# ``for .. in`` is not supported 23af6ab5fSopenharmony_ci 33af6ab5fSopenharmony_ciRule ``arkts-no-for-in`` 43af6ab5fSopenharmony_ci 53af6ab5fSopenharmony_ci**Severity: error** 63af6ab5fSopenharmony_ci 73af6ab5fSopenharmony_ciArkTS does not support the iteration over object contents by the 83af6ab5fSopenharmony_ci``for .. in`` loop. For objects, iteration over properties at runtime is 93af6ab5fSopenharmony_ciconsidered redundant because object layout is known at compile time, and 103af6ab5fSopenharmony_cicannot change at runtime. For arrays, iterate with the regular ``for`` loop. 113af6ab5fSopenharmony_ci 123af6ab5fSopenharmony_ci 133af6ab5fSopenharmony_ci## TypeScript 143af6ab5fSopenharmony_ci 153af6ab5fSopenharmony_ci 163af6ab5fSopenharmony_ci``` 173af6ab5fSopenharmony_ci 183af6ab5fSopenharmony_ci let a: number[] = [1.0, 2.0, 3.0] 193af6ab5fSopenharmony_ci for (let i in a) { 203af6ab5fSopenharmony_ci console.log(a[i]) 213af6ab5fSopenharmony_ci } 223af6ab5fSopenharmony_ci 233af6ab5fSopenharmony_ci``` 243af6ab5fSopenharmony_ci 253af6ab5fSopenharmony_ci## ArkTS 263af6ab5fSopenharmony_ci 273af6ab5fSopenharmony_ci 283af6ab5fSopenharmony_ci``` 293af6ab5fSopenharmony_ci 303af6ab5fSopenharmony_ci let a: number[] = [1.0, 2.0, 3.0] 313af6ab5fSopenharmony_ci for (let i = 0; i < a.length; ++i) { 323af6ab5fSopenharmony_ci console.log(a[i]) 333af6ab5fSopenharmony_ci } 343af6ab5fSopenharmony_ci 353af6ab5fSopenharmony_ci``` 363af6ab5fSopenharmony_ci 373af6ab5fSopenharmony_ci## See also 383af6ab5fSopenharmony_ci 393af6ab5fSopenharmony_ci- Recipe 082: ``for-of`` is supported only for arrays, strings, sets, maps and classes derived from them (``arkts-for-of-str-arr``) 403af6ab5fSopenharmony_ci 413af6ab5fSopenharmony_ci 42