events.js

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

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]
    }
  }