Exercise 27: Events

Directions

Create an 'eventing' library out of the Events class. The Events class should have methods 'on', 'trigger', and 'off'.

Guidelines

Solution

class Events {
  constructor(){
    this.events = {};
  }

  // Register an event handler
  on(eventName, callback) {
    if (this.events[eventName]){
      this.events[eventName].push(callback);
    } else {
      this.events[eventName] = [callback];
    }
  }

  // Trigger all callbacks associated
  // with a given eventName
  trigger(eventName) {
    if (this.events[eventName]){
      for (let cb of this.events[eventName]){
        cb();
      }
    }
  }

  // Remove all event handlers associated
  // with the given eventName
  off(eventName) {
    delete this.events[eventName];
  }
}