window.fetchp

The global fetchp function is fetch-like interface to JSONP API.

Installation

$ bower install naderio/fetchp

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

$ bower install es6-promise

THE REST IS NOT UPDATED

Usage

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

HTML

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

JSON

fetchp('/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

fetchp('/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')

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

Post JSON

fetchp('/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')

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

Caveats

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

• The Promise returned from fetchp() 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, fetchp 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 fetchp 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()
}

fetchp('/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:

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

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

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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