arantes555electron-fetch
A light-weight module that brings window.fetch to Electron's background process.
Forked from node-fetch.
Motivation
Instead of implementing XMLHttpRequest over Electron's net module to run browser-specific Fetch polyfill, why not go from native net.request to fetch API directly? Hence electron-fetch, minimal code for a window.fetch compatible API on Electron's background runtime.
Why not simply use node-fetch? Well, Electron's net module does a better job than Node.js' http module at handling web proxies.
Features
- Stay consistent with
window.fetchAPI. - Runs on both Electron and Node.js, using either Electron's
netmodule, or Node.jshttpmodule as backend. - Make conscious trade-off when following whatwg fetch spec and stream spec implementation details, document known difference.
- Use native promise.
- Use native stream for body, on both request and response.
- Decode content encoding (gzip/deflate) properly, and convert string output (such as
res.text()andres.json()) to UTF-8 automatically. - Useful extensions such as timeout, redirect limit (when running on Node.js), response size limit, [explicit errors][] for troubleshooting.
Difference from client-side fetch
- See Known Differences for details.
- If you happen to use a missing feature that
window.fetchoffers, feel free to open an issue. - Pull requests are welcomed too!
Difference from node-fetch
- Removed node-fetch specific options, such as
compression. - Added electron-specific options to specify the
Session& to enable using cookies from it. - Added electron-specific option
useElectronNet, which can be set to false when running on Electron in order to behave as Node.js. - Removed possibility to use custom Promise implementation (it's 2018,
Promiseis available everywhere!). - Removed the possibility to forbid content compression (incompatible with Electron's
netmodule, and of limited interest) standard-ized the code.
Install
$ npm install electron-fetch --save
Usage
import fetch from 'electron-fetch'
// or
// const fetch = require('electron-fetch').default
// plain text or html
fetch('https://github.com/')
.then(res => res.text())
.then(body => console.log(body))
// json
fetch('https://api.github.com/users/github')
.then(res => res.json())
.then(json => console.log(json))
// catching network error
// 3xx-5xx responses are NOT network errors, and should be handled in then()
// you only need one catch() at the end of your promise chain
fetch('http://domain.invalid/')
.catch(err => console.error(err))
// stream
// the node.js way is to use stream when possible
fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
.then(res => {
const dest = fs.createWriteStream('./octocat.png')
res.body.pipe(dest)
})
// buffer
// if you prefer to cache binary data in full, use buffer()
// note that buffer() is a electron-fetch only API
import fileType from 'file-type'
fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
.then(res => res.buffer())
.then(buffer => fileType(buffer))
.then(type => { /* ... */ })
// meta
fetch('https://github.com/')
.then(res => {
console.log(res.ok)
console.log(res.status)
console.log(res.statusText)
console.log(res.headers.raw())
console.log(res.headers.get('content-type'))
})
// post
fetch('http://httpbin.org/post', { method: 'POST', body: 'a=1' })
.then(res => res.json())
.then(json => console.log(json))
// post with stream from file
import { createReadStream } from 'fs'
const stream = createReadStream('input.txt')
fetch('http://httpbin.org/post', { method: 'POST', body: stream })
.then(res => res.json())
.then(json => console.log(json))
// post with JSON
const body = { a: 1 }
fetch('http://httpbin.org/post', {
method: 'POST',
body: JSON.stringify(body),
headers: { 'Content-Type': 'application/json' },
})
.then(res => res.json())
.then(json => console.log(json))
// post with form-data (detect multipart)
import FormData from 'form-data'
const form = new FormData()
form.append('a', 1)
fetch('http://httpbin.org/post', { method: 'POST', body: form })
.then(res => res.json())
.then(json => console.log(json))
// post with form-data (custom headers)
// note that getHeaders() is non-standard API
import FormData from 'form-data'
const form = new FormData()
form.append('a', 1)
fetch('http://httpbin.org/post', { method: 'POST', body: form, headers: form.getHeaders() })
.then(res => res.json())
.then(json => console.log(json))
// node 7+ with async function
(async function () {
const res = await fetch('https://api.github.com/users/github')
const json = await res.json()
console.log(json)
})()
// providing proxy credentials (electron-specific)
fetch(url, {
onLogin (authInfo) { // this 'authInfo' is the one received by the 'login' event. See https://www.electronjs.org/docs/latest/api/client-request#event-login
return Promise.resolve({ username: 'testuser', password: 'testpassword' })
}
})
See test cases for more examples.
API
fetch(url[, options])
urlA string representing the URL for fetchingoptionsOptions for the HTTP(S) request- Returns:
Promise<Response>
Perform an HTTP(S) fetch.
url should be an absolute url, such as http://example.com/. A path-relative URL (/file/under/root) or protocol-relative URL (//can-be-http-or-https.com/) will result in a rejected promise.
Options
The default values are shown after each option key.
const defaultOptions = {
// These properties are part of the Fetch Standard
method: 'GET',
headers: {}, // request headers. format is the identical to that accepted by the Headers constructor (see below)
body: null, // request body. can be null, a string, a Buffer, a Blob, or a Node.js Readable stream
redirect: 'follow', // (/!\ only works when running on Node.js) set to `manual` to extract redirect headers, `error` to reject redirect
signal: null, // the AbortSignal from an AbortController instance.
// The following properties are electron-fetch extensions
follow: 20, // (/!\ only works when running on Node.js) maximum redirect count. 0 to not follow redirect
timeout: 0, // req/res timeout in ms, it resets on redirect. 0 to disable (OS limit applies)
size: 0, // maximum response body size in bytes. 0 to disable
session: session.defaultSession, // (/!\ only works when running on Electron) Electron Session object.,
agent: null, // (/!\ only works when useElectronNet is false) Node HTTP Agent.,
useElectronNet: true, // When running on Electron, defaults to true. On Node.js, defaults to false and cannot be set to true.
useSessionCookies: true, // (/!\ only works when running on Electron >= 7) Whether or not to automatically send cookies from session.,
user: undefined, // When running on Electron behind an authenticated HTTP proxy, username to use to authenticate
password: undefined, // When running on Electron behind an authenticated HTTP proxy, password to use to authenticate
onLogin: undefined // When running on Electron behind an authenticated HTTP proxy, handler of electron.ClientRequest's login event. Can be used for acquiring proxy credentials in an async manner (e.g. prompting the user). Receives an `AuthInfo` object, and must return a `Promise<{ username: string, password: string }>`.
}
Default Headers
If no values are set, the following request headers will be sent automatically:
| Header | Value |
|---|---|
Accept-Encoding |
gzip,deflate |
Accept |
*/* |
Connection |
close |
Content-Length |
(automatically calculated, if possible) |
User-Agent |
electron-fetch/1.0 (+https://github.com/arantes555/electron-fetch) |
Class: Request
An HTTP(S) request containing information about URL, method, headers, and the body. This class implements the Body interface.
Due to the nature of Node.js, the following properties are not implemented at this moment:
typedestinationreferrerreferrerPolicymodecredentialscacheintegritykeepalive
The following electron-fetch extension properties are provided:
follow(/!\ only works when running on Node.js)counter(/!\ only works when running on Node.js)session(/!\ only works when running on Electron)agent(/!\ only works when running on Node.js)useElectronNet(/!\ only works when running on Electron, throws when set to true on Node.js)useSessionCookies(/!\ only works when running on Electron >= 7. For electron < 11, it saves received cookies regardless of this option, but only sends them if true. For electron >= 11, it saves them only if true.)
See options for exact meaning of these extensions.
new Request(input[, options])
(spec-compliant)
inputA string representing a URL, or anotherRequest(which will be cloned)options[Options][#fetch-options] for the HTTP(S) request
Constructs a new Request object. The constructor is identical to that in the browser.
In most cases, directly fetch(url, options) is simpler than creating a Request object.
Class: Response
An HTTP(S) response. This class implements the Body interface.
The following properties are not implemented in electron-fetch at this moment:
Response.error()Response.redirect()typeredirectedtrailer
new Response([body[, options]])
(spec-compliant)
bodyA string or Readable streamoptionsAResponseInitoptions dictionary
Constructs a new Response object. The constructor is identical to that in the browser.
Because Node.js & Electron's background do not implement service workers (for which this class was designed), one rarely has to construct a Response directly.
Class: Headers
This class allows manipulating and iterating over a set of HTTP headers. All methods specified in the Fetch Standard are implemented.
new Headers([init])
(spec-compliant)
initOptional argument to pre-fill theHeadersobject
Construct a new Headers object. init can be either null, a Headers object, an key-value map object, or any iterable object.
// Example adapted from https://fetch.spec.whatwg.org/#example-headers-class
const meta = {
'Content-Type': 'text/xml',
'Breaking-Bad': '<3'
}
const headers = new Headers(meta)
// The above is equivalent to
const meta = [
[ 'Content-Type', 'text/xml' ],
[ 'Breaking-Bad', '<3' ]
]
const headers = new Headers(meta)
// You can in fact use any iterable objects, like a Map or even another Headers
const meta = new Map()
meta.set('Content-Type', 'text/xml')
meta.set('Breaking-Bad', '<3')
const headers = new Headers(meta)
const copyOfHeaders = new Headers(headers)
Interface: Body
Body is an abstract interface with methods that are applicable to both Request and Response classes.
The following methods are not yet implemented in electron-fetch at this moment:
formData()
body.body
(deviation from spec)
- Node.js
Readablestream
The data encapsulated in the Body object. Note that while the Fetch Standard requires the property to always be a WHATWG ReadableStream, in electron-fetch it is a Node.js Readable stream.
body.bodyUsed
(spec-compliant)
Boolean
A boolean property for if this body has been consumed. Per spec, a consumed body cannot be used again.
body.arrayBuffer()
body.blob()
body.json()
body.text()
(spec-compliant)
- Returns:
Promise
Consume the body and return a promise that will resolve to one of these formats.
body.buffer()
(electron-fetch extension)
- Returns:
Promise<Buffer>
Consume the body and return a promise that will resolve to a Buffer.
body.textConverted()
(electron-fetch extension)
- Returns:
Promise<String>
Identical to body.text(), except instead of always converting to UTF-8, encoding sniffing will be performed and text converted to UTF-8, if possible.
Class: FetchError
(electron-fetch extension)
An operational error in the fetching process. See ERROR-HANDLING.md for more info.
License
MIT
Acknowledgement
Thanks to github/fetch for providing a solid implementation reference. Thanks to node-fetch for providing a solid base to fork.