- [Post data using a file stream](#post-data-using-a-file-stream)
- [Post with form-data (detect multipart)](#post-with-form-data-detect-multipart)
- [Request cancellation with AbortSignal](#request-cancellation-with-abortsignal)
- [API](#api)
- [fetch(url[, options])](#fetchurl-options)
- [Options](#options)
- [Class: Request](#class-request)
- [Class: Response](#class-response)
- [Class: Headers](#class-headers)
- [Interface: Body](#interface-body)
- [Class: FetchError](#class-fetcherror)
- [License](#license)
- [Acknowledgement](#acknowledgement)
<!-- /TOC -->
## Motivation
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.
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).
## Features
- Stay consistent with `window.fetch` API.
- Make conscious trade-off when following [WHATWG fetch spec][whatwg-fetch] and [stream spec](https://streams.spec.whatwg.org/) implementation details, document known differences.
- Use native promise, but allow substituting it with [insert your favorite promise library].
- Use native Node streams 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, response size limit, [explicit errors](ERROR-HANDLING.md) for troubleshooting.
## Difference from client-side fetch
- See [Known Differences](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!
## Installation
Current stable release (`2.x`)
```sh
$ npm install node-fetch --save
```
## Loading and configuring the module
We suggest you load the module via `require`, pending the stabalizing of es modules in node:
```js
const fetch = require('node-fetch');
```
If you are using a Promise library other than native, set it through fetch.Promise:
```js
const Bluebird = require('bluebird');
fetch.Promise = Bluebird;
```
## Common Usage
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.
.then(res => res.json()) // expecting a json response
.then(json => console.log(json));
```
#### Post with JSON
```js
const body = { a: 1 };
fetch('https://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 parameters
`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.
NOTE: The `Content-Type` header is only set automatically to `x-www-form-urlencoded` when an instance of `URLSearchParams` is given as such:
NOTE: 3xx-5xx responses are *NOT* exceptions, and should be handled in `then()`, see the next section.
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.
```js
fetch('https://domain.invalid/')
.catch(err => console.error(err));
```
#### Handling client and server errors
It is common to create a helper function to check that the response contains no client (4xx) or server (5xx) error responses:
```js
function checkStatus(res) {
if (res.ok) { // res.status >= 200 && res.status <300
return res;
} else {
throw MyCustomError(res.statusText);
}
}
fetch('https://httpbin.org/status/400')
.then(checkStatus)
.then(res => console.log('will not get here...'))
```
## Advanced Usage
#### Streams
The "Node.js way" is to use streams when possible:
`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.
<aid="fetch-options"></a>
### Options
The default values are shown after each option key.
```js
{
// 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', // set to `manual` to extract redirect headers, `error` to reject redirect
signal: null, // pass an instance of AbortSignal to optionally abort requests
// The following properties are node-fetch extensions
follow: 20, // 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). Signal is recommended instead.
compress: true, // support gzip/deflate content encoding. false to disable
size: 0, // maximum response body size in bytes. 0 to disable
Note: when `body` is a `Stream`, `Content-Length` is not set automatically.
##### Custom Agent
The `agent` option allows you to specify networking related options that's out of the scope of Fetch. Including and not limit to:
- Support self-signed certificate
- Use only IPv4 or IPv6
- Custom DNS Lookup
See [`http.Agent`](https://nodejs.org/api/http.html#http_new_agent_options) for more information.
In addition, `agent` option accepts a function that returns http(s).Agent instance given current [URL](https://nodejs.org/api/url.html), this is useful during a redirection chain across HTTP and HTTPS protocol.
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 node-fetch extension properties are provided:
-`follow`
-`compress`
-`counter`
-`agent`
See [options](#fetch-options) for exact meaning of these extensions.
#### new Request(input[, options])
<small>*(spec-compliant)*</small>
-`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.
<aid="class-response"></a>
### Class: Response
An HTTP(S) response. This class implements the [Body](#iface-body) interface.
The following properties are not implemented in node-fetch at this moment:
-`Response.error()`
-`Response.redirect()`
-`type`
-`trailer`
#### new Response([body[, options]])
<small>*(spec-compliant)*</small>
-`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 does not implement service workers (for which this class was designed), one rarely has to construct a `Response` directly.
#### response.ok
<small>*(spec-compliant)*</small>
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.
Convenience property representing if the request has been redirected at least once. Will evaluate to true if the internal redirect counter is greater than 0.
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])
<small>*(spec-compliant)*</small>
-`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);
```
<aid="iface-body"></a>
### 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 node-fetch at this moment:
-`formData()`
#### body.body
<small>*(deviation from spec)*</small>
* 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 node-fetch it is a Node.js [`Readable` stream][node-readable].
#### body.bodyUsed
<small>*(spec-compliant)*</small>
*`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()
<small>*(spec-compliant)*</small>
* Returns: <code>Promise</code>
Consume the body and return a promise that will resolve to one of these formats.
#### body.buffer()
<small>*(node-fetch extension)*</small>
* Returns: <code>Promise<Buffer></code>
Consume the body and return a promise that will resolve to a Buffer.
#### body.textConverted()
<small>*(node-fetch extension)*</small>
* Returns: <code>Promise<String></code>
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.
(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.)
<aid="class-fetcherror"></a>
### Class: FetchError
<small>*(node-fetch extension)*</small>
An operational error in the fetching process. See [ERROR-HANDLING.md][] for more info.
<aid="class-aborterror"></a>
### Class: AbortError
<small>*(node-fetch extension)*</small>
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.
## Acknowledgement
Thanks to [github/fetch](https://github.com/github/fetch) for providing a solid implementation reference.
`node-fetch` v1 was maintained by [@bitinn](https://github.com/bitinn); v2 was maintained by [@TimothyGu](https://github.com/timothygu), [@bitinn](https://github.com/bitinn) and [@jimmywarting](https://github.com/jimmywarting); v2 readme is written by [@jkantr](https://github.com/jkantr).
