typed-event-emitter

typed-event-emitter

This module provides an alternative API than the well known event emitting interfaces used in the browser (DOM) or node.js. Instead of accepting arbitrary strings as the event name, this module forces you to register your events in your class. Consequently, the style of binding and emitting events differs a little bit, ensuring already at binding time that the events actually exists.

Usage

Take a look at the following snippet (TypeScript):

import { EventEmitter } from 'typed-event-emitter';

class MyClass extends EventEmitter {
  onValueChanged = this.registerEvent<(newValue: number) => any>();
  
  private _value: number;
  
  constructor(value: number) {
    // initialize EventEmitter
    super();
    
    this._value = value;
  }
  
  get value() {
    return this._value;
  }
  
  set value(value: number) {
    this._value = value;
    this.emit(this.onValueChanged, this._value);
  }
}

let instance = new MyClass();
instance.onValueChanged(newValue => {
  console.log(`Value changed: ${newValue}`);
});

instance.value = 27;

First the EventEmitter is loaded from the module. Next, any class, that shall emit events, must extend that EventEmitter. If your class has its own constructor, make sure to call super().

Any events, your class could emit, must be registered in the form:

onFooBar = this.registerEvent<callbackType>();

Where onFooBar can be any name (it doesn't need to begin with on) and callbackType must be the type of the function the listeners must have. With this, you can see the signature your function must have when you're about to bind a listener to that event.

To fire/emit an event (only possible from within your event emitter), you have to call this.emit(this.onFooBar, ...), where this.onFooBar is the event to emit and ... any number of parameters, that will be passed to the listeners.

License

typed-event-emitter is licensed under the ISC License.