94 lines
3.6 KiB
Markdown
94 lines
3.6 KiB
Markdown
# EventEmitter3
|
|
|
|
[](https://www.npmjs.com/package/eventemitter3)[](https://travis-ci.org/primus/eventemitter3)[](https://david-dm.org/primus/eventemitter3)[](https://coveralls.io/r/primus/eventemitter3?branch=master)[](https://webchat.freenode.net/?channels=primus)
|
|
|
|
[](https://saucelabs.com/u/eventemitter3)
|
|
|
|
EventEmitter3 is a high performance EventEmitter. It has been micro-optimized
|
|
for various of code paths making this, one of, if not the fastest EventEmitter
|
|
available for Node.js and browsers. The module is API compatible with the
|
|
EventEmitter that ships by default with Node.js but there are some slight
|
|
differences:
|
|
|
|
- Domain support has been removed.
|
|
- We do not `throw` an error when you emit an `error` event and nobody is
|
|
listening.
|
|
- The `newListener` and `removeListener` events have been removed as they
|
|
are useful only in some uncommon use-cases.
|
|
- The `setMaxListeners`, `getMaxListeners`, `prependListener` and
|
|
`prependOnceListener` methods are not available.
|
|
- Support for custom context for events so there is no need to use `fn.bind`.
|
|
- The `removeListener` method removes all matching listeners, not only the
|
|
first.
|
|
|
|
It's a drop in replacement for existing EventEmitters, but just faster. Free
|
|
performance, who wouldn't want that? The EventEmitter is written in EcmaScript 3
|
|
so it will work in the oldest browsers and node versions that you need to
|
|
support.
|
|
|
|
## Installation
|
|
|
|
```bash
|
|
$ npm install --save eventemitter3
|
|
```
|
|
|
|
## CDN
|
|
|
|
Recommended CDN:
|
|
|
|
```text
|
|
https://unpkg.com/eventemitter3@latest/umd/eventemitter3.min.js
|
|
```
|
|
|
|
## Usage
|
|
|
|
After installation the only thing you need to do is require the module:
|
|
|
|
```js
|
|
var EventEmitter = require('eventemitter3');
|
|
```
|
|
|
|
And you're ready to create your own EventEmitter instances. For the API
|
|
documentation, please follow the official Node.js documentation:
|
|
|
|
http://nodejs.org/api/events.html
|
|
|
|
### Contextual emits
|
|
|
|
We've upgraded the API of the `EventEmitter.on`, `EventEmitter.once` and
|
|
`EventEmitter.removeListener` to accept an extra argument which is the `context`
|
|
or `this` value that should be set for the emitted events. This means you no
|
|
longer have the overhead of an event that required `fn.bind` in order to get a
|
|
custom `this` value.
|
|
|
|
```js
|
|
var EE = new EventEmitter()
|
|
, context = { foo: 'bar' };
|
|
|
|
function emitted() {
|
|
console.log(this === context); // true
|
|
}
|
|
|
|
EE.once('event-name', emitted, context);
|
|
EE.on('another-event', emitted, context);
|
|
EE.removeListener('another-event', emitted, context);
|
|
```
|
|
|
|
### Tests and benchmarks
|
|
|
|
This module is well tested. You can run:
|
|
|
|
- `npm test` to run the tests under Node.js.
|
|
- `npm run test-browser` to run the tests in real browsers via Sauce Labs.
|
|
|
|
We also have a set of benchmarks to compare EventEmitter3 with some available
|
|
alternatives. To run the benchmarks run `npm run benchmark`.
|
|
|
|
Tests and benchmarks are not included in the npm package. If you want to play
|
|
with them you have to clone the GitHub repository.
|
|
Note that you will have to run an additional `npm i` in the benchmarks folder
|
|
before `npm run benchmark`.
|
|
|
|
## License
|
|
|
|
[MIT](LICENSE)
|