window.fetch polyfill

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

Usage

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

HTML

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

Post form

var form = document.querySelector('form')

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

Post form fields

fetch('/query', {
  method: 'post',
  body: {
    name: 'Hubot',
    login: 'hubot'
  }
})

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

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