fetch is undefined in React Native

[tgamauf]

I've written an API wrapper that uses cross-fetch to make it compatible with Browsers, Node and React Native. Now, if I test it with Node it works perfectly, but if I use the wrapper in React Native if fails with the following error: TypeError: undefined is not a function (evaluating 'cross_fetch_1.default(url, init)'). If I print the type of cross_fetch_1 I get:

{ [Function]
   polyfill: true,
  Response: { [Function: Response] error: [Function], redirect: [Function] },
  Request: [Function: Request],
  Headers: [Function: Headers] }

and "undefined" for either cross_fetch_1.default or cross_fetch_1.fetch.

The library was developed in Typescript, so the cross_fetch_1 variable is created by the TS compiler. You can find the Typescript code here https://github.com/tgamauf/onetimesecret-api/blob/1b8edff66bde11807c8ff7d29030b4d3e6661277/lib/request.ts#L150 and the compiled JS here https://github.com/tgamauf/onetimesecret-api/blob/1b8edff66bde11807c8ff7d29030b4d3e6661277/lib/request.js#L179.

As far as I can tell I am using the module as it is supposed to be used. What could cause this?

[mattmccutchen]

Also reported here. cross-fetch should probably add a default export to browser-ponyfill.js, just as node-ponyfill.js has.

[tgamauf]

As Matt noted in the Stackoverflow question, activating esModuleInterop in the Typescript compiler is a workaround. I agree, this should be fixed as it isn't really expected behavior.

[sondremare]

@lquixada Do you have an estimate of when this will be released?

[lquixada]

@sondremare hopefully this weekend.