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https://github.com/arantes555/electron-fetch

A light-weight module that brings window.fetch to the background process of Electron
https://github.com/arantes555/electron-fetch

electron fetch hacktoberfest http https

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A light-weight module that brings window.fetch to the background process of Electron

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electron-fetch

==========



[![npm version][npm-image]][npm-url]

[![build status][travis-image]][travis-url]

[![coverage status][codecov-image]][codecov-url]



A light-weight module that brings `window.fetch` to Electron's background process.

Forked from [`node-fetch`](https://github.com/bitinn/node-fetch).



## Motivation



Instead of implementing `XMLHttpRequest` over Electron's `net` module to run browser-specific [Fetch polyfill](https://github.com/github/fetch), 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.fetch` API.

- Runs on both Electron and Node.js, using either Electron's `net` module, or Node.js `http` module as backend.

- Make conscious trade-off when following [whatwg fetch spec][whatwg-fetch] and [stream spec](https://streams.spec.whatwg.org/) 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()` and `res.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](https://github.com/arantes555/electron-fetch/blob/master/LIMITS.md) for details.

- If you happen to use a missing feature that `window.fetch` offers, 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, `Promise` is available everywhere!).

- Removed the possibility to forbid content compression (incompatible with Electron's `net` module, and of limited interest)

- [`standard`-ized](http://standardjs.com) the code.



## Install



```sh

$ npm install electron-fetch --save

```



## Usage



```javascript

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](https://github.com/arantes555/electron-fetch/blob/master/test/test.js) for more examples.



## API



### fetch(url[, options])



- `url` A string representing the URL for fetching

- `options` [Options](#fetch-options) for the HTTP(S) request

- Returns: Promise<[Response](#class-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.



```js

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 }>`.

}

```



If no agent is specified, the default agent provided by Node.js is used. Note that [this changed in Node.js 19](https://github.com/nodejs/node/blob/4267b92604ad78584244488e7f7508a690cb80d0/lib/_http_agent.js#L564) to have `keepalive` true by default. If you wish to enable `keepalive` in an earlier version of Node.js, you can override the agent as per the following code sample.



##### Default Headers



If no values are set, the following request headers will be sent automatically:



| Header            | Value                                                                |

|-------------------|----------------------------------------------------------------------|

| `Accept-Encoding` | `gzip,deflate`                                                       |

| `Accept`          | `*/*`                                                                |

| `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](#iface-body) interface.



Due to the nature of Node.js, the following properties are not implemented at this moment:



- `type`

- `destination`

- `referrer`

- `referrerPolicy`

- `mode`

- `credentials`

- `cache`

- `integrity`

- `keepalive`



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](#fetch-options) for exact meaning of these extensions.



#### new Request(input[, options])



*(spec-compliant)*



- `input` A string representing a URL, or another `Request` (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](https://developer.mozilla.org/en-US/docs/Web/API/Request/Request).



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](#iface-body) interface.



The following properties are not implemented in electron-fetch at this moment:



- `Response.error()`

- `Response.redirect()`

- `type`

- `redirected`

- `trailer`



#### new Response([body[, options]])



*(spec-compliant)*



- `body` A string or [Readable stream][node-readable]

- `options` A [`ResponseInit`][response-init] options dictionary



Constructs a new `Response` object. The constructor is identical to that in the [browser](https://developer.mozilla.org/en-US/docs/Web/API/Response/Response).



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][whatwg-fetch] are implemented.



#### new Headers([init])



*(spec-compliant)*



- `init` Optional argument to pre-fill the `Headers` object



Construct a new `Headers` object. `init` can be either `null`, a `Headers` object, an key-value map object, or any iterable object.



```js

// 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 [`Readable` stream][node-readable]



The data encapsulated in the `Body` object. Note that while the [Fetch Standard][whatwg-fetch] requires the property to always be a WHATWG `ReadableStream`, in electron-fetch it is a Node.js [`Readable` stream][node-readable].



#### 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](https://github.com/github/fetch) for providing a solid implementation reference.

Thanks to [node-fetch](https://github.com/bitinn/node-fetch) for providing a solid base to fork.



[npm-image]: https://img.shields.io/npm/v/electron-fetch.svg?style=flat-square

[npm-url]: https://www.npmjs.com/package/electron-fetch

[travis-image]: https://img.shields.io/travis/com/arantes555/electron-fetch.svg?style=flat-square

[travis-url]: https://travis-ci.com/arantes555/electron-fetch

[codecov-image]: https://img.shields.io/codecov/c/github/arantes555/electron-fetch.svg?style=flat-square

[codecov-url]: https://codecov.io/gh/arantes555/electron-fetch

[ERROR-HANDLING.md]: https://github.com/arantes555/electron-fetch/blob/master/ERROR-HANDLING.md

[whatwg-fetch]: https://fetch.spec.whatwg.org/

[response-init]: https://fetch.spec.whatwg.org/#responseinit

[node-readable]: https://nodejs.org/api/stream.html#stream_readable_streams

[mdn-headers]: https://developer.mozilla.org/en-US/docs/Web/API/Headers