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# engine.io-parser
[![Build Status](https://github.com/socketio/engine.io-parser/workflows/CI/badge.svg?branch=main)](https://github.com/socketio/engine.io-parser/actions)
[![NPM version](https://badge.fury.io/js/engine.io-parser.svg)](https://npmjs.com/package/engine.io-parser)
This is the JavaScript parser for the engine.io protocol encoding,
shared by both
[engine.io-client](https://github.com/socketio/engine.io-client) and
[engine.io](https://github.com/socketio/engine.io).
## How to use
### Standalone
The parser can encode/decode packets, payloads, and payloads as binary
with the following methods: `encodePacket`, `decodePacket`, `encodePayload`,
`decodePayload`.
Example:
```js
const parser = require("engine.io-parser");
const data = Buffer.from([ 1, 2, 3, 4 ]);
parser.encodePacket({ type: "message", data }, encoded => {
const decodedData = parser.decodePacket(encoded); // decodedData === data
});
```
### With browserify
Engine.IO Parser is a commonjs module, which means you can include it by using
`require` on the browser and package using [browserify](http://browserify.org/):
1. install the parser package
```shell
npm install engine.io-parser
```
1. write your app code
```js
const parser = require("engine.io-parser");
const testBuffer = new Int8Array(10);
for (let i = 0; i < testBuffer.length; i++) testBuffer[i] = i;
const packets = [{ type: "message", data: testBuffer.buffer }, { type: "message", data: "hello" }];
parser.encodePayload(packets, encoded => {
parser.decodePayload(encoded,
(packet, index, total) => {
const isLast = index + 1 == total;
if (!isLast) {
const buffer = new Int8Array(packet.data); // testBuffer
} else {
const message = packet.data; // "hello"
}
});
});
```
1. build your app bundle
```bash
$ browserify app.js > bundle.js
```
1. include on your page
```html
<script src="/path/to/bundle.js"></script>
```
## Features
- Runs on browser and node.js seamlessly
- Runs inside HTML5 WebWorker
- Can encode and decode packets
- Encodes from/to ArrayBuffer or Blob when in browser, and Buffer or ArrayBuffer in Node
## API
Note: `cb(type)` means the type is a callback function that contains a parameter of type `type` when called.
### Node
- `encodePacket`
- Encodes a packet.
- **Parameters**
- `Object`: the packet to encode, has `type` and `data`.
- `data`: can be a `String`, `Number`, `Buffer`, `ArrayBuffer`
- `Boolean`: binary support
- `Function`: callback, returns the encoded packet (`cb(String)`)
- `decodePacket`
- Decodes a packet. Data also available as an ArrayBuffer if requested.
- Returns data as `String` or (`Blob` on browser, `ArrayBuffer` on Node)
- **Parameters**
- `String` | `ArrayBuffer`: the packet to decode, has `type` and `data`
- `String`: optional, the binary type
- `encodePayload`
- Encodes multiple messages (payload).
- If any contents are binary, they will be encoded as base64 strings. Base64
encoded strings are marked with a b before the length specifier
- **Parameters**
- `Array`: an array of packets
- `Function`: callback, returns the encoded payload (`cb(String)`)
- `decodePayload`
- Decodes data when a payload is maybe expected. Possible binary contents are
decoded from their base64 representation.
- **Parameters**
- `String`: the payload
- `Function`: callback, returns (cb(`Object`: packet, `Number`:packet index, `Number`:packet total))
## Tests
Standalone tests can be run with `npm test` which will run the node.js tests.
Browser tests are run using [zuul](https://github.com/defunctzombie/zuul).
(You must have zuul setup with a saucelabs account.)
You can run the tests locally using the following command:
```
npm run test:browser
```
## Support
The support channels for `engine.io-parser` are the same as `socket.io`:
- irc.freenode.net **#socket.io**
- [Github Discussions](https://github.com/socketio/socket.io/discussions)
- [Website](https://socket.io)
## Development
To contribute patches, run tests or benchmarks, make sure to clone the
repository:
```bash
git clone git://github.com/socketio/engine.io-parser.git
```
Then:
```bash
cd engine.io-parser
npm ci
```
See the `Tests` section above for how to run tests before submitting any patches.
## License
MIT