Changes from original

The original library was changed to support the following:

• Converted to UMD support.
• Module returns a function that contains, as static properties, the respective polyfill: Headers, Request, Response and fetch. Calling this function directly with an object on input will add those polyfills components to the given object.
• Support for .abort()
• Support for onProgress input options. Ability to monitor content being uploaded

These items above make this version of the library non-standard. A little more about the change:

UMD Support

Adds support for AMD (define), module.exports as well as polyfill of global object. When global object is polyfilled, Global object will also have a property called fetchPolyfill which holds the functionality of this library (case you would like to use it instead of the version provided nativelly).

Support for .abort

The promise returned from .fetch() will have an additional method called abort that can be called to abort an inflight request.

Support for onProgress

An input option of onProgress can be defined to monitor upload activity. Option should be a Function whic is called every time the xhr.upload object triggers an progress event.

Examples

defined(["fetch"], function(fetchPolyfill){
    var fetch = fetchPolyfill.fetch;
    ...
})

Load in the browser where .fetch() API alrady exists:

window.fetchPolyfill.fetch();// call polyfill .fetch()

Add the fetch method and associated Classes to a given object. Use it to extend your classes.

var myObject = {};
window.fetchPolyfill(myObject);

window.fetch polyfill

This project adheres to the [Open Code of Conduct][code-of-conduct]. By participating, you are expected to uphold this code. [code-of-conduct]: http://todogroup.org/opencodeofconduct/#fetch/[email protected]

The global fetch function is an easier way to make web requests and handle responses than using an XMLHttpRequest. This polyfill is written as closely as possible to the standard Fetch specification at https://fetch.spec.whatwg.org.

Installation

Available on Bower as fetch.

$ bower install fetch

You'll also need a Promise polyfill for older browsers.

$ bower install es6-promise

This can also be installed with npm.

$ npm install whatwg-fetch --save

For a node.js implementation, try node-fetch.

For use with webpack, refer to Using WebPack with shims and polyfills.

Usage

The fetch function supports any HTTP method. We'll focus on GET and POST example requests.

HTML

fetch('/users.html')
  .then(function(response) {
    return response.text()
  }).then(function(body) {
    document.body.innerHTML = body
  })

JSON

fetch('/users.json')
  .then(function(response) {
    return response.json()
  }).then(function(json) {
    console.log('parsed json', json)
  }).catch(function(ex) {
    console.log('parsing failed', ex)
  })

Response metadata

fetch('/users.json').then(function(response) {
  console.log(response.headers.get('Content-Type'))
  console.log(response.headers.get('Date'))
  console.log(response.status)
  console.log(response.statusText)
})

Post form

var form = document.querySelector('form')

fetch('/users', {
  method: 'post',
  body: new FormData(form)
})

Post JSON

fetch('/users', {
  method: 'post',
  headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    name: 'Hubot',
    login: 'hubot',
  })
})

File upload

var input = document.querySelector('input[type="file"]')

var data = new FormData()
data.append('file', input.files[0])
data.append('user', 'hubot')

fetch('/avatars', {
  method: 'post',
  body: data
})

Caveats

The fetch specification differs from jQuery.ajax() in mainly two ways that bear keeping in mind:

• The Promise returned from fetch() won't reject on HTTP error status even if the response is a HTTP 404 or 500. Instead, it will resolve normally, and it will only reject on network failure, or if anything prevented the request from completing.

• By default, fetch won't send any cookies to the server, resulting in unauthenticated requests if the site relies on maintaining a user session.

Handling HTTP error statuses

To have fetch Promise reject on HTTP error statuses, i.e. on any non-2xx status, define a custom response handler:

function checkStatus(response) {
  if (response.status >= 200 && response.status < 300) {
    return response
  } else {
    var error = new Error(response.statusText)
    error.response = response
    throw error
  }
}

function parseJSON(response) {
  return response.json()
}

fetch('/users')
  .then(checkStatus)
  .then(parseJSON)
  .then(function(data) {
    console.log('request succeeded with JSON response', data)
  }).catch(function(error) {
    console.log('request failed', error)
  })

Sending cookies

To automatically send cookies for the current domain, the credentials option must be provided:

fetch('/users', {
  credentials: 'same-origin'
})

This option makes fetch behave similar to XMLHttpRequest with regards to cookies. Otherwise, cookies won't get sent, resulting in these requests not preserving the authentication session.

Use the include value to send cookies in a cross-origin resource sharing (CORS) request.

fetch('https://example.com:1234/users', {
  credentials: 'include'
})

Receiving cookies

Like with XMLHttpRequest, the Set-Cookie response header returned from the server is a forbidden header name and therefore can't be programatically read with response.headers.get(). Instead, it's the browser's responsibility to handle new cookies being set (if applicable to the current URL). Unless they are HTTP-only, new cookies will be available through document.cookie.

Obtaining the Response URL

Due to limitations of XMLHttpRequest, the response.url value might not be reliable after HTTP redirects on older browsers.

The solution is to configure the server to set the response HTTP header X-Request-URL to the current URL after any redirect that might have happened. It should be safe to set it unconditionally.

# Ruby on Rails controller example
response.headers['X-Request-URL'] = request.url

This server workaround is necessary if you need reliable response.url in Firefox < 32, Chrome < 37, Safari, or IE.

Browser Support

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