abortcontroller-polyfill

Minimal stubs so that the AbortController DOM API for terminating ``fetch()`` requests can be used in browsers that doesn't yet implement it. This "polyfill" doesn't actually close the connection when the request is aborted, but it will call ``.catch()` with `err.name == 'AbortError'` instead of `.then()``.

const controller = new AbortController();
const signal = controller.signal;
fetch('/some/url', {signal})
  .then(res => res.json())
  .then(data => {
    // do something with "data"
  }).catch(err => {
    if (err.name == 'AbortError') {
      return;
    }
  });
// controller.abort(); // can be called at any time

You can read about the AbortController API in the DOM specification.

$ npm install --save abortcontroller-polyfill

If you're using webpack or similar, you then import it early in your client entrypoint .js file using

import 'abortcontroller-polyfill/dist/polyfill-patch-fetch'
// or:
require('abortcontroller-polyfill/dist/polyfill-patch-fetch')

Using it on browsers without fetch

If you need to support browsers where fetch is not available at all (for example Internet Explorer 11), you first need to install a fetch polyfill and then import the ``abortcontroller-polyfill`` afterwards.
The unfetch npm package offers a minimal ``fetch()` implementation (though it does not offer for example a `Request`` class). If you need a polyfill that implements the full Fetch specification, use the whatwg-fetch npm package instead. Typically you will also need to load a polyfill that implements ES6 promises, for example promise-polyfill, and of course you need to avoid ES6 arrow functions and template literals.
Example projects showing abortable fetch setup so that it works even in Internet Explorer 11, using both unfetch and GitHub fetch, is available here.

Using it along with 'create-react-app'

create-react-app enforces the no-undef eslint rule at compile time so if your version of eslint does not list ``AbortController`` etc as a known global for the ``browser`` environment, then you might run into an compile error like:

'AbortController' is not defined  no-undef

This can be worked around by (temporarily, details here) adding a declaration like:

const AbortController = window.AbortController;

Using the AbortController/AbortSignal without patching fetch

If you just want to polyfill AbortController/AbortSignal without patching fetch you can use:

import 'abortcontroller-polyfill/dist/abortcontroller-polyfill-only'

You can either import it as a ponyfill without modifying globals:

const { AbortController, abortableFetch } = require('abortcontroller-polyfill/dist/cjs-ponyfill');
const { fetch } = abortableFetch(require('node-fetch'));
// or
// import { AbortController, abortableFetch } from 'abortcontroller-polyfill/dist/cjs-ponyfill';
// import _fetch from 'node-fetch';
// const { fetch } = abortableFetch(_fetch);

or if you're lazy

global.fetch = require('node-fetch');
require('abortcontroller-polyfill/dist/polyfill-patch-fetch');

If you also need a ``Request`` class with support for aborting you can do:

const { AbortController, abortableFetch } = require('abortcontroller-polyfill/dist/cjs-ponyfill');
const _nodeFetch = require('node-fetch');
const { fetch, Request } = abortableFetch({fetch: _nodeFetch, Request: _nodeFetch.Request});

const controller = new AbortController();
const signal = controller.signal;
controller.abort();
fetch(Request("http://api.github.com", {signal}))
  .then(r => r.json())
  .then(j => console.log(j))
  .catch(err => {
      if (err.name === 'AbortError') {
          console.log('aborted');
      }
  })

See also Node.js examples hereThe ``abortcontroller-polyfill`` works on Internet Explorer 11. However, to use it you must first install separate polyfills for promises and for ``fetch()``. For the promise polyfill, you can use the ``promise-polyfill` package from npm, and for `fetch()` you can use either the `whatwg-fetch` npm package (complete fetch implementation) or the `unfetch`` npm package (not a complete polyfill but it's only 500 bytes large and covers a lot of the basic use cases).
If you choose ``unfetch``, the imports should be done in this order for example:

import 'promise-polyfill/src/polyfill';
import 'unfetch/polyfill';
import 'abortcontroller-polyfill';

See example code here.The ``abortcontroller-polyfill` works on Internet Explorer 8. However, since `github-fetch` only supports IE 10+ you need to use the `fetch-ie8`` npm package instead and also note that IE 8 only implements ES 3 so you need to use the ``es5-shim`` package (or similar). Finally, just like with IE 11 you also need to polyfill promises. One caveat is that CORS requests will not work out of the box on IE 8.
Here is a basic example of abortable fetch running in IE 8.

• Martin Olsson
• Jimmy Wärting
• silverwind
• Rasmus Jacobsen
• João Vieira
• Cyril Auburtin
• Leonardo Apiwan
• Jake Champion
• Sai Srinivasan
• Ambar Lee

MIT