CallbackCollection-JS

function CallbackNumber(val){
    var _value = val;
    var callbacks = [];
        this.addCallback = function (callbackFn){
        callbacks.push(entry);
        };
        this.triggerCallbacks =  function(){
            for(var i = 0 ; i < callbacks.length ; i++ ){
            callbacks[i].call(this);
            }
    };
    this.getValue = function(){
            return _value
        };
    this.setValue = function(val){
            if(_value != val){
                    _value  = val;
                    this.triggerCallbacks();
            }
        };
}
// -------- test Code ----------//
var num1 = new CallbackNumber(1);
var num2 = new CallbackNumber(2);
num1.addCallback(function(){console.log("num1's Callback called");});
num2.addCallback(function(){console.log("num2's Callback called");});
num2.setValue(6) // num2's Callback called

// Test - 1
num2.addCallback(function(){console.log(num1.getValue());});
num2.setValue(22)
// num2's callback called
// 22

// Test - 2
num2.addCallback(num1.getValue.bind(num1));
num2.setValue(8);
// num2's callback called
// 1