npm install whatwg-fetch --save

import 'whatwg-fetch'

window.fetch(...)

import {fetch as fetchPolyfill} from 'whatwg-fetch'

window.fetch(...)   // use native browser version
fetchPolyfill(...)  // use polyfill implementation

entry: ['whatwg-fetch', ...]

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

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)
  })

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)
})

var form = document.querySelector('form')

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

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

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
})