apollo-link-rest: "Headers is not defined" occur when using apollo-link-rest in weixin mini program

Here’s what ended up working for me:

import clientFetch from 'unfetch';
import serverFetch, { Headers as ServerHeaders } from 'node-fetch';

const client = typeof document !== 'undefined';
global.Headers = client ? global.Headers : ServerHeaders;
const customFetch = client ? clientFetch : serverFetch;

const acmeLink = new JsonApiLink({
  …
  credentials: 'same-origin',
  customFetch,
});

I was able to fix this issue by using custom fetch

import fetch from "isomorphic-fetch"

const restLink = new RestLink({
  uri: "https://...",
  customFetch: fetch,
  headers: {
    "Content-Type": "application/json",
  },
})

@fbartho Hi! I’m facing this problem on ios 9.3.5.I tried import the fetch-headers polyfill but not work. I found that the header instance from fetch-headers doesn’t have the forEach method(see below).

Is there any other solutions?

I solved this problem by using the fetch polyfill.

import * as Polyfillheaders from 'fetch-headers'
import fetch from 'isomorphic-unfetch'

// hook in the Headers polyfill for your environment!
global.Headers = global.Headers || Polyfillheaders;

function customFetch(url, options) {
  const headers = options.headers.entries().reduce((accumulator, h) => {
    accumulator[h[0]] = h[1]
    return accumulator
  }, {})
  return fetch(url, { ...options, headers })
}

const restLink = new RestLink({
  uri: CONTENTFUL_CONTENT_DELIVERY_API,
  customFetch,
})

Something like the above might do the trick @2wheelcoder

@VinSpee 's solution worked for me for a Gatsby JS application as well.

Thanks @VinSpee —this was exactly what I needed