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

If you don't use the var keyword, "blabla" becomes a global variable. At other points in the code if you also use blabla without var, it will also be global, and you can accidentally change other instances of blabla and introduce unintended bugs in your code. "var" puts the variable in the current scope, so in the case above, it's only accessible to Foo.