var Person = function(name) {

  this.name = name;

​

  // lets assign this to that :)

  var that = this;

  this.sayHi = function() {

    // That is used to call the foo property

    alert(that.name);

  };

};

​

​

var ahmad = new Person('Ahmad');

var element = document.getElementById('button');

element.addEventListener('click', ahmad.sayHi); // => Ahmad