EventBus.js

eventbus.js

class EventBus {
  constructor() {
    this.listeners = {};
  }

  addEventListener(type, callback, scope) {
    let args = [];
    const numOfArgs = arguments.length;

    for(let i=0; i < numOfArgs; i++){
      args.push(arguments[i]);
    }
    args = args.length > 3 ? args.splice(3, args.length-1) : [];

    if(typeof this.listeners[type] != "undefined") {
      this.listeners[type].push({scope:scope, callback:callback, args:args});
    } else {
      this.listeners[type] = [{scope:scope, callback:callback, args:args}];
    }
  }

  removeEventListener(type, callback, scope) {
    if (typeof this.listeners[type] != "undefined") {
      const numOfCallbacks = this.listeners[type].length;
      const newArray = [];

      for(let i=0; i<numOfCallbacks; i++) {
        const listener = this.listeners[type][i];
        if(listener.scope === scope && listener.callback === callback) {
        } else {
          newArray.push(listener);
        }
      }

      this.listeners[type] = newArray;
    }
  }

  dispatch(type, target) {
    const event = {
      type: type,
      target: target
    };
    let args = [];
    const numOfArgs = arguments.length;

    for(let i=0; i < numOfArgs; i++){
      args.push(arguments[i]);
    }

    args = args.length > 2 ? args.splice(2, args.length-1) : [];
    args = [event].concat(args);

    if (typeof this.listeners[type] != "undefined") {
      const listeners = this.listeners[type].slice();
      const numOfCallbacks = listeners.length;

      for(let i=0; i<numOfCallbacks; i++) {
        let listener = listeners[i];

        if (listener && listener.callback) {
          const concatArgs = args.concat(listener.args);
          listener.callback.apply(listener.scope, concatArgs);
        }
      }
    }
  }
}