Shows variable/function scope in JavaScript

function_scope_example.js

function Foo(args) {
  var private_variable = args.private_var;
  this.public_variable = args.public_var;
  
  this.public_method = function () { };
  function private_method() { }
}

object_inheritance_example.js

function Foo() {
  this.doOneThing = function () { return 'one done.'; };
}
var foo = new Foo();

function Bar() {
  this.doAnotherThing = function () { return 'another done.'; };
}

var bar = new Bar();
bar.doOneThing()      //=> TypeError: undefined is not a function (#doOneThing is undefined)
bar.doAnotherThing()  //=> 'another done.'

Bar.prototype = foo;  // Prototyping is like inheritance, but more flexible
                      // Can't do Bar.prototype Foo(), must use an actual instance, like foo or new Foo()

bar.doOneThing()      //=> same TypeError as before

var bar2 = new Bar();
bar2.doOneThing();    //=> 'one done.' -- It works!
bar2.doAnotherThing() //=> 'another done.'