shrine-medco/shrine-webclient/src/main/js/client/js-shrine/jspm_packages/github/github/fetch@1.0.0afec901a0acdmaster
fetch@1.0.0
README.md
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/opensource@github.com
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.
sh $ bower install fetch
You'll also need a Promise polyfill for older browsers.
sh $ bower install es6-promise
This can also be installed with npm.
sh $ 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.
For babel and es2015+, make sure to import the file:
javascript import 'whatwg-fetch'; fetch(...);
Usage
The fetch function supports any HTTP method. We'll focus on GET and POST example requests.
HTML
javascript fetch('/users.html') .then(function(response) { return response.text() }).then(function(body) { document.body.innerHTML = body })
JSON
javascript 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
javascript 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
javascript var form = document.querySelector('form') fetch('/users', { method: 'POST', body: new FormData(form) })
Post JSON
javascript fetch('/users', { method: 'POST', headers: { 'Accept': 'application/json', 'Content-Type': 'application/json' }, body: JSON.stringify({ name: 'Hubot', login: 'hubot', }) })
File upload
javascript 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:
javascript 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:
javascript 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.
javascript 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.
[forbidden header name]: https://developer.mozilla.org/en-US/docs/Glossary/Forbidden_header_name
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 # 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
!Chrome | !Firefox | !IE | !Opera | !Safari
- | --- | --- | --- | --- |
Latest ✔ | Latest ✔ | 10+ ✔ | Latest ✔ | 6.1+ ✔ |