Simple library to work with custom events.
- Simple event emitter API:
on
,off
,emit
,hasEventHandler
. - Event emitter API is chainable.
- Events can be emitted with multiple attached parameters.
- Data about emitted event are wrapped into an object with uniform structure that is passed to handlers.
- Ability to add event handler that should be called just once.
- Ability to enhance prototype of constructor function (class) with event emitter API (emitter methods can be mixed in
prototype
). - Available as ECMAScript 6/2015 module, CommonJS module or UMD.
- Work in any ECMAScript 3+ environment (browsers, Node.js etc).
- Small.
Installation ↑
npm install neva
bower install neva
Use dist/neva.js
or dist/neva.min.js
(minified version).
Usage ↑
import getEmitter from 'neva';
const getEmitter = require('neva').getEmitter;
define(['path/to/dist/neva.js'], function(neva) {
const getEmitter = neva.getEmitter;
});
<!-- Use bower_components/neva/dist/neva.js if the library was installed by Bower -->
<script type="text/javascript" src="path/to/dist/neva.js"></script>
<script type="text/javascript">
// neva is available via neva field of window object
const getEmitter = neva.getEmitter;
</script>
Examples ↑
const emitter = getEmitter();
const eventHandler = (event) => {
console.log('eventHandler: event type -', event.type, ', data -', event.data);
};
const obj = {
name: 'obj',
handler(event) {
console.log(`${this.name}.handler: event type -`, event.type, ', params -', event.params);
}
};
function onceHandler(event) {
console.log('onceHandler: event type -', event.type, ', data -', event.data);
}
emitter.on(['event1', 'event2'], eventHandler)
.on('event1', obj.handler, obj)
.on('event2', onceHandler, null, {once: true});
emitter.emit('event1', 1, 2, 3)
.emit({type: 'event2', data: 'some data', qty: 8});
// The following will be printed into console:
// eventHandler: event type - event1 , data - 1
// obj.handler: event type - event1 , params - Array [ 1, 2, 3 ]
// eventHandler: event type - event2 , data - some data
// onceHandler: event type - event2 , data - some data
emitter.hasEventHandler('event1', eventHandler); // true
emitter.hasEventHandler('event2', onceHandler); // false
emitter.off('event1', eventHandler);
emitter.hasEventHandler('event1', eventHandler); // false
emitter.hasEventHandler('event1'); // true
emitter.off('event1');
emitter.hasEventHandler('event1'); // false
emitter.hasEventHandler(); // true
emitter.off();
emitter.hasEventHandler(); // false
class SomeClass {
...
}
// Add event emitter methods to class
getEmitter(SomeClass.prototype);
API ↑
Create event emitter or add methods to work with events into specified object.
target
can be prototype of some constructor function (class).
on(type: string | string[], handler: Function, [context: Object], [settings: HandlerSettings]): EventEmitter
Register a handler for the specified event type(s).
Remove the specified event handler.
Remove all handlers for the given event type.
Remove all registered event handlers.
Call all handlers for the specified event type.
An object with the following fields will be passed in each handler:
type: string
- the event type (value oftype
parameter).params: Array
- list of additional parameters that are passed besides the event type ([param1, param2, ...]
).data: any
- value of the second function's parameter (value ofparams[0]
).
Call all handlers for the specified event type and pass the given object in each handler.
Check whether the specified event handler is registered.
Check whether any handler for the specified event type is registered.
Check whether any event handler is registered.
See docs
for details.
Contributing ↑
In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using Grunt.
License ↑
Copyright (c) 2017-2021 Denis Sikuler
Licensed under the MIT license.