What happens with “var” variables inside a JavaScript Constructor?

Question

example:

function Foo() {
    this.bla = 1;
    var blabla = 10;
    blablabla = 100;
    this.getBlabla = function () { 
        return blabla; // exposes b         


        

Answer 1

It will become a local (think of 'private') variable within Foo(). Meaning that you can't access it outside of Foo().

function Foo() {
  this.bla = 1; // this becomes an extension of Foo()
  var blabla = 10; // this becomes a "Local" (sort of like a 'private') variable
}

You could expose it (by returning it) with a Foo method.

function Foo() {
    var blabla = 10; // local

    this.getBlabla = function () { 
        return blabla; // exposes blabla outside
    }
}

Now outside of Foo():

var FooBar = new Foo();

var what_is_blabla = FooBar.getBlabla(); //what_is_blabla will be 10

jsFiddle demonstration