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534 lines
17 KiB
534 lines
17 KiB
node-fetch
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==========
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[![npm version][npm-image]][npm-url]
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[![build status][travis-image]][travis-url]
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[![coverage status][codecov-image]][codecov-url]
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[![install size][install-size-image]][install-size-url]
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A light-weight module that brings `window.fetch` to Node.js
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(We are looking for [v2 maintainers and collaborators](https://github.com/bitinn/node-fetch/issues/567))
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<!-- TOC -->
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- [Motivation](#motivation)
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- [Features](#features)
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- [Difference from client-side fetch](#difference-from-client-side-fetch)
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- [Installation](#installation)
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- [Loading and configuring the module](#loading-and-configuring-the-module)
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- [Common Usage](#common-usage)
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- [Plain text or HTML](#plain-text-or-html)
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- [JSON](#json)
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- [Simple Post](#simple-post)
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- [Post with JSON](#post-with-json)
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- [Post with form parameters](#post-with-form-parameters)
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- [Handling exceptions](#handling-exceptions)
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- [Handling client and server errors](#handling-client-and-server-errors)
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- [Advanced Usage](#advanced-usage)
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- [Streams](#streams)
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- [Buffer](#buffer)
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- [Accessing Headers and other Meta data](#accessing-headers-and-other-meta-data)
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- [Post data using a file stream](#post-data-using-a-file-stream)
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- [Post with form-data (detect multipart)](#post-with-form-data-detect-multipart)
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- [Request cancellation with AbortSignal](#request-cancellation-with-abortsignal)
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- [API](#api)
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- [fetch(url[, options])](#fetchurl-options)
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- [Options](#options)
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- [Class: Request](#class-request)
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- [Class: Response](#class-response)
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- [Class: Headers](#class-headers)
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- [Interface: Body](#interface-body)
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- [Class: FetchError](#class-fetcherror)
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- [License](#license)
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- [Acknowledgement](#acknowledgement)
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<!-- /TOC -->
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## Motivation
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Instead of implementing `XMLHttpRequest` in Node.js to run browser-specific [Fetch polyfill](https://github.com/github/fetch), why not go from native `http` to `fetch` API directly? Hence `node-fetch`, minimal code for a `window.fetch` compatible API on Node.js runtime.
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See Matt Andrews' [isomorphic-fetch](https://github.com/matthew-andrews/isomorphic-fetch) or Leonardo Quixada's [cross-fetch](https://github.com/lquixada/cross-fetch) for isomorphic usage (exports `node-fetch` for server-side, `whatwg-fetch` for client-side).
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## Features
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- Stay consistent with `window.fetch` API.
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- Make conscious trade-off when following [WHATWG fetch spec][whatwg-fetch] and [stream spec](https://streams.spec.whatwg.org/) implementation details, document known differences.
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- Use native promise, but allow substituting it with [insert your favorite promise library].
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- Use native Node streams for body, on both request and response.
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- Decode content encoding (gzip/deflate) properly, and convert string output (such as `res.text()` and `res.json()`) to UTF-8 automatically.
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- Useful extensions such as timeout, redirect limit, response size limit, [explicit errors](ERROR-HANDLING.md) for troubleshooting.
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## Difference from client-side fetch
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- See [Known Differences](LIMITS.md) for details.
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- If you happen to use a missing feature that `window.fetch` offers, feel free to open an issue.
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- Pull requests are welcomed too!
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## Installation
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Current stable release (`2.x`)
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```sh
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$ npm install node-fetch --save
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```
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## Loading and configuring the module
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We suggest you load the module via `require`, pending the stabalizing of es modules in node:
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```js
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const fetch = require('node-fetch');
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```
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If you are using a Promise library other than native, set it through fetch.Promise:
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```js
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const Bluebird = require('bluebird');
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fetch.Promise = Bluebird;
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```
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## Common Usage
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NOTE: The documentation below is up-to-date with `2.x` releases, [see `1.x` readme](https://github.com/bitinn/node-fetch/blob/1.x/README.md), [changelog](https://github.com/bitinn/node-fetch/blob/1.x/CHANGELOG.md) and [2.x upgrade guide](UPGRADE-GUIDE.md) for the differences.
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#### Plain text or HTML
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```js
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fetch('https://github.com/')
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.then(res => res.text())
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.then(body => console.log(body));
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```
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#### JSON
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```js
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fetch('https://api.github.com/users/github')
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.then(res => res.json())
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.then(json => console.log(json));
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```
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#### Simple Post
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```js
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fetch('https://httpbin.org/post', { method: 'POST', body: 'a=1' })
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.then(res => res.json()) // expecting a json response
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.then(json => console.log(json));
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```
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#### Post with JSON
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```js
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const body = { a: 1 };
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fetch('https://httpbin.org/post', {
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method: 'post',
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body: JSON.stringify(body),
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headers: { 'Content-Type': 'application/json' },
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})
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.then(res => res.json())
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.then(json => console.log(json));
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```
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#### Post with form parameters
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`URLSearchParams` is available in Node.js as of v7.5.0. See [official documentation](https://nodejs.org/api/url.html#url_class_urlsearchparams) for more usage methods.
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NOTE: The `Content-Type` header is only set automatically to `x-www-form-urlencoded` when an instance of `URLSearchParams` is given as such:
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```js
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const { URLSearchParams } = require('url');
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const params = new URLSearchParams();
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params.append('a', 1);
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fetch('https://httpbin.org/post', { method: 'POST', body: params })
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.then(res => res.json())
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.then(json => console.log(json));
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```
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#### Handling exceptions
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NOTE: 3xx-5xx responses are *NOT* exceptions, and should be handled in `then()`, see the next section.
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Adding a catch to the fetch promise chain will catch *all* exceptions, such as errors originating from node core libraries, like network errors, and operational errors which are instances of FetchError. See the [error handling document](ERROR-HANDLING.md) for more details.
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```js
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fetch('https://domain.invalid/')
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.catch(err => console.error(err));
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```
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#### Handling client and server errors
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It is common to create a helper function to check that the response contains no client (4xx) or server (5xx) error responses:
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```js
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function checkStatus(res) {
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if (res.ok) { // res.status >= 200 && res.status < 300
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return res;
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} else {
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throw MyCustomError(res.statusText);
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}
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}
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fetch('https://httpbin.org/status/400')
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.then(checkStatus)
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.then(res => console.log('will not get here...'))
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```
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## Advanced Usage
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#### Streams
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The "Node.js way" is to use streams when possible:
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```js
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fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
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.then(res => {
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const dest = fs.createWriteStream('./octocat.png');
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res.body.pipe(dest);
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});
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```
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#### Buffer
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If you prefer to cache binary data in full, use buffer(). (NOTE: buffer() is a `node-fetch` only API)
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```js
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const fileType = require('file-type');
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fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
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.then(res => res.buffer())
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.then(buffer => fileType(buffer))
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.then(type => { /* ... */ });
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```
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#### Accessing Headers and other Meta data
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```js
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fetch('https://github.com/')
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.then(res => {
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console.log(res.ok);
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console.log(res.status);
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console.log(res.statusText);
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console.log(res.headers.raw());
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console.log(res.headers.get('content-type'));
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});
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```
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#### Post data using a file stream
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```js
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const { createReadStream } = require('fs');
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const stream = createReadStream('input.txt');
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fetch('https://httpbin.org/post', { method: 'POST', body: stream })
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.then(res => res.json())
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.then(json => console.log(json));
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```
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#### Post with form-data (detect multipart)
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```js
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const FormData = require('form-data');
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const form = new FormData();
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form.append('a', 1);
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fetch('https://httpbin.org/post', { method: 'POST', body: form })
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.then(res => res.json())
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.then(json => console.log(json));
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// OR, using custom headers
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// NOTE: getHeaders() is non-standard API
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const form = new FormData();
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form.append('a', 1);
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const options = {
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method: 'POST',
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body: form,
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headers: form.getHeaders()
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}
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fetch('https://httpbin.org/post', options)
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.then(res => res.json())
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.then(json => console.log(json));
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```
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#### Request cancellation with AbortSignal
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> NOTE: You may only cancel streamed requests on Node >= v8.0.0
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You may cancel requests with `AbortController`. A suggested implementation is [`abort-controller`](https://www.npmjs.com/package/abort-controller).
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An example of timing out a request after 150ms could be achieved as follows:
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```js
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import AbortController from 'abort-controller';
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const controller = new AbortController();
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const timeout = setTimeout(
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() => { controller.abort(); },
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150,
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);
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fetch(url, { signal: controller.signal })
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.then(res => res.json())
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.then(
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data => {
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useData(data)
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},
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err => {
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if (err.name === 'AbortError') {
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// request was aborted
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}
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},
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)
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.finally(() => {
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clearTimeout(timeout);
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});
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```
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See [test cases](https://github.com/bitinn/node-fetch/blob/master/test/test.js) for more examples.
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## API
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### fetch(url[, options])
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- `url` A string representing the URL for fetching
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- `options` [Options](#fetch-options) for the HTTP(S) request
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- Returns: <code>Promise<[Response](#class-response)></code>
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Perform an HTTP(S) fetch.
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`url` should be an absolute url, such as `https://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.
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<a id="fetch-options"></a>
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### Options
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The default values are shown after each option key.
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```js
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{
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// These properties are part of the Fetch Standard
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method: 'GET',
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headers: {}, // request headers. format is the identical to that accepted by the Headers constructor (see below)
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body: null, // request body. can be null, a string, a Buffer, a Blob, or a Node.js Readable stream
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redirect: 'follow', // set to `manual` to extract redirect headers, `error` to reject redirect
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signal: null, // pass an instance of AbortSignal to optionally abort requests
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// The following properties are node-fetch extensions
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follow: 20, // maximum redirect count. 0 to not follow redirect
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timeout: 0, // req/res timeout in ms, it resets on redirect. 0 to disable (OS limit applies). Signal is recommended instead.
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compress: true, // support gzip/deflate content encoding. false to disable
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size: 0, // maximum response body size in bytes. 0 to disable
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agent: null // http(s).Agent instance, allows custom proxy, certificate, dns lookup etc.
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}
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```
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##### Default Headers
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If no values are set, the following request headers will be sent automatically:
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Header | Value
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------------------- | --------------------------------------------------------
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`Accept-Encoding` | `gzip,deflate` _(when `options.compress === true`)_
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`Accept` | `*/*`
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`Connection` | `close` _(when no `options.agent` is present)_
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`Content-Length` | _(automatically calculated, if possible)_
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`Transfer-Encoding` | `chunked` _(when `req.body` is a stream)_
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`User-Agent` | `node-fetch/1.0 (+https://github.com/bitinn/node-fetch)`
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<a id="class-request"></a>
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### Class: Request
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An HTTP(S) request containing information about URL, method, headers, and the body. This class implements the [Body](#iface-body) interface.
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Due to the nature of Node.js, the following properties are not implemented at this moment:
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- `type`
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- `destination`
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- `referrer`
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- `referrerPolicy`
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- `mode`
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- `credentials`
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- `cache`
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- `integrity`
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- `keepalive`
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The following node-fetch extension properties are provided:
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- `follow`
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- `compress`
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- `counter`
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- `agent`
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See [options](#fetch-options) for exact meaning of these extensions.
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#### new Request(input[, options])
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<small>*(spec-compliant)*</small>
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- `input` A string representing a URL, or another `Request` (which will be cloned)
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- `options` [Options][#fetch-options] for the HTTP(S) request
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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).
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In most cases, directly `fetch(url, options)` is simpler than creating a `Request` object.
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<a id="class-response"></a>
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### Class: Response
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An HTTP(S) response. This class implements the [Body](#iface-body) interface.
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The following properties are not implemented in node-fetch at this moment:
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- `Response.error()`
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- `Response.redirect()`
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- `type`
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- `redirected`
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- `trailer`
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#### new Response([body[, options]])
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<small>*(spec-compliant)*</small>
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- `body` A string or [Readable stream][node-readable]
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- `options` A [`ResponseInit`][response-init] options dictionary
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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).
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Because Node.js does not implement service workers (for which this class was designed), one rarely has to construct a `Response` directly.
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#### response.ok
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<small>*(spec-compliant)*</small>
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Convenience property representing if the request ended normally. Will evaluate to true if the response status was greater than or equal to 200 but smaller than 300.
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<a id="class-headers"></a>
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### Class: Headers
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This class allows manipulating and iterating over a set of HTTP headers. All methods specified in the [Fetch Standard][whatwg-fetch] are implemented.
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#### new Headers([init])
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<small>*(spec-compliant)*</small>
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- `init` Optional argument to pre-fill the `Headers` object
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Construct a new `Headers` object. `init` can be either `null`, a `Headers` object, an key-value map object, or any iterable object.
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```js
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// Example adapted from https://fetch.spec.whatwg.org/#example-headers-class
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const meta = {
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'Content-Type': 'text/xml',
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'Breaking-Bad': '<3'
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};
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const headers = new Headers(meta);
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// The above is equivalent to
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const meta = [
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[ 'Content-Type', 'text/xml' ],
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[ 'Breaking-Bad', '<3' ]
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];
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const headers = new Headers(meta);
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// You can in fact use any iterable objects, like a Map or even another Headers
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const meta = new Map();
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meta.set('Content-Type', 'text/xml');
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meta.set('Breaking-Bad', '<3');
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const headers = new Headers(meta);
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const copyOfHeaders = new Headers(headers);
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```
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<a id="iface-body"></a>
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### Interface: Body
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`Body` is an abstract interface with methods that are applicable to both `Request` and `Response` classes.
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The following methods are not yet implemented in node-fetch at this moment:
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- `formData()`
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#### body.body
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<small>*(deviation from spec)*</small>
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* Node.js [`Readable` stream][node-readable]
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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 node-fetch it is a Node.js [`Readable` stream][node-readable].
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#### body.bodyUsed
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<small>*(spec-compliant)*</small>
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* `Boolean`
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A boolean property for if this body has been consumed. Per spec, a consumed body cannot be used again.
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#### body.arrayBuffer()
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#### body.blob()
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#### body.json()
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#### body.text()
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<small>*(spec-compliant)*</small>
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* Returns: <code>Promise</code>
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Consume the body and return a promise that will resolve to one of these formats.
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#### body.buffer()
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<small>*(node-fetch extension)*</small>
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* Returns: <code>Promise<Buffer></code>
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Consume the body and return a promise that will resolve to a Buffer.
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#### body.textConverted()
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<small>*(node-fetch extension)*</small>
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* Returns: <code>Promise<String></code>
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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.
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(This API requires an optional dependency on npm package [encoding](https://www.npmjs.com/package/encoding), which you need to install manually. `webpack` users may see [a warning message](https://github.com/bitinn/node-fetch/issues/412#issuecomment-379007792) due to this optional dependency.)
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<a id="class-fetcherror"></a>
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### Class: FetchError
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<small>*(node-fetch extension)*</small>
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An operational error in the fetching process. See [ERROR-HANDLING.md][] for more info.
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<a id="class-aborterror"></a>
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### Class: AbortError
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<small>*(node-fetch extension)*</small>
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An Error thrown when the request is aborted in response to an `AbortSignal`'s `abort` event. It has a `name` property of `AbortError`. See [ERROR-HANDLING.MD][] for more info.
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## Acknowledgement
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Thanks to [github/fetch](https://github.com/github/fetch) for providing a solid implementation reference.
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`node-fetch` v1 was maintained by [@bitinn](https://github.com/bitinn), v2 is currently maintained by [@TimothyGu](https://github.com/timothygu), v2 readme is written by [@jkantr](https://github.com/jkantr).
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## License
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MIT
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[npm-image]: https://img.shields.io/npm/v/node-fetch.svg?style=flat-square
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[npm-url]: https://www.npmjs.com/package/node-fetch
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[travis-image]: https://img.shields.io/travis/bitinn/node-fetch.svg?style=flat-square
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[travis-url]: https://travis-ci.org/bitinn/node-fetch
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[codecov-image]: https://img.shields.io/codecov/c/github/bitinn/node-fetch.svg?style=flat-square
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[codecov-url]: https://codecov.io/gh/bitinn/node-fetch
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[install-size-image]: https://flat.badgen.net/packagephobia/install/node-fetch
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[install-size-url]: https://packagephobia.now.sh/result?p=node-fetch
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[whatwg-fetch]: https://fetch.spec.whatwg.org/
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[response-init]: https://fetch.spec.whatwg.org/#responseinit
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[node-readable]: https://nodejs.org/api/stream.html#stream_readable_streams
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[mdn-headers]: https://developer.mozilla.org/en-US/docs/Web/API/Headers
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[LIMITS.md]: https://github.com/bitinn/node-fetch/blob/master/LIMITS.md
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[ERROR-HANDLING.md]: https://github.com/bitinn/node-fetch/blob/master/ERROR-HANDLING.md
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[UPGRADE-GUIDE.md]: https://github.com/bitinn/node-fetch/blob/master/UPGRADE-GUIDE.md
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