Question

Say I have a javascript function/class called Foo and it has a property called bar. I want the value of bar to be supplied when the class is instantiated, e.g:

var myFoo = new Foo(5);

would set myFoo.bar to 5.

If I make bar a public variable, then this works, e.g:

function Foo(bar)
{
    this.bar = bar;
}

But if I want to make it private, e.g:

function Foo(bar)
{
   var bar;
}

Then how would I set the value of the private variable bar such that its available to all internal functions of foo?

Answer 1

You have to put all functions that need to access the private variable inside the constructor:

function Foo(bar)
{
  //bar is inside a closure now, only these functions can access it
  this.setBar = function() {bar = 5;}
  this.getBar = function() {return bar;}
  //Other functions
}

var myFoo = new Foo(5);
myFoo.bar;      //Undefined, cannot access variable closure
myFoo.getBar(); //Works, returns 5