@kevinwin/

EventEmitter

JavaScript

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main.js
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class EventEmitter {
  constructor() {
    this._events = {};
  }

  // returns an unsubscribe function, which when called removes the
  // callback's association with the event
  subscribe(event, fn) {
    if (this._events[event] === undefined) {
      this._events[event] = [];
    }

    this._events[event].push(fn);

    return () => {
      this._events[event] = this._events[event].filter(eventFn => eventFn !== fn);
    }
  }

  // emits all functions associated with a given event plus any arguments passed
  emit(event, ...args) {
    if (this._events[event]) {
      const functions = this._events[event];

      functions.forEach(fn => {
        fn(...args);
      })
    }
  }
}
Native Browser JavaScript