undefined is not a function(evaluating '_iterator[typeof Symbol === "function"?Symbol.iterator:"@@iterator"]()')

[hzuhyb]

I used "for(let...of...){}" to traverse a Map object at react-native，I got this error.
it's working perfectly for IOS and android debug mode, but not working for android normal mode.

[leebyron]

Unfortunately this bit of code you're running into is not part of Immutable.js, but is instead an issue with Babel transpilation.

Android's JS runtime defines Symbol, however does not define Symbol.iterator - updating to a later version of JSC or Babel will likely fix your issue.

[ayessymkanov]

@leebyron what is JSC?

[ayessymkanov]

@huangtubiao have you solved the issue?

[hzuhyb]

@ayessymkanov facebook/react-native#15902

[Runtime007]

import 'core-js/es6/symbol'; import 'core-js/fn/symbol/iterator';

it works for me.

[CodingJbz]

@Runtime007 thank you . it works for me . but why it works.
@Runtime007 it's will cause other issue . eg: BackHandler can't work in product env.

[ericketts]

@CodingJbz do you have any links regarding the BackHandler bug? Is it introduced by including the core-js polyfills?

[rgoldiez]

@Runtime007 - your solution works, but why is it needed, and only on Android?

[ericketts]

@rgoldiez that polyfills Symbol and iterator stuff that's missing out of the box on android

[adirzoari]

@Runtime007 where to make these imports?
I have same issue.