// Create an event bus
function Bus() {
  let eventFuncObject={};
  
  function on(eventName, eventFunc){

    if(!eventFuncObject[eventName]){
      eventFuncObject[eventName]=[];
    }
    eventFuncObject[eventName].push(eventFunc);
  }
  
  function off(eventName){
    delete eventFuncObject[eventName];
  }
  
  function trigger(eventName){
    let argumetsArry = [];

    eventFuncObject[eventName].map(eventFunc=>{

      Object.keys(arguments).map(argKey=>{
        if(argKey !== '0'){
          argumetsArry.push(arguments[argKey]);
        }          
      })
      
      eventFunc(...argumetsArry);
    });
  }  

  this.on = on;
  this.off = off;
  this.trigger = trigger;
}

var handler = new Bus();

handler.on('click', function () {
  console.log('on click was triggered');
})

handler.on('click', function () {
  console.log('another handler');
})

handler.on('sum', function (a, b) {
   var sum = a + b;
   console.log(sum);
});


handler.trigger('click');
// console.log's 2 statements

handler.off('click');

// handler.trigger('click');
handler.trigger('sum',3,4,5);

handler.trigger('sum',3,8,5,5);
// nothing happens