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) for isomorphic usage (exports `node-fetch` for server-side, `whatwg-fetch` for client-side).
- Make conscious trade-off when following [whatwg fetch spec][whatwg-fetch] and [stream spec](https://streams.spec.whatwg.org/) implementation details, document known difference.
`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.
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`
-`redirected`
-`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.
<aid="class-headers"></a>
### 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])
<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.
<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.