JavaScript : Object-Oriented Programming

Private variables

Closures are frequently used to encapsulate some information as private variables. JavaScript does not allow such encapsulation found in programming languages such as Java or C++, but by using closures, we can achieve similar encapsulation:

function privateTest(){
  var points=0;
  this.getPoints=function(){
    return points;
  };
  this.score=function(){
    points++;
  };
}

var private = new privateTest();
private.score();
console.log(private.points); // undefined
console.log(private.getPoints());

In the preceding example, we are creating a function that we intend to call as a constructor. In this privateTest() function, we are creating a var points=0 variable as a function-scoped variable. This variable is available only in privateTest(). Additionally, ...