Just one simple example about private and public methods in JavaScript.

Check this code in JS:

(function (ns) {
	function myCreator () {
		var self=this;
		
		function privateMethod() {
			alert("Hi I am private method and I can be executed only within myCreator class (I will be never called)");
		}
		
		self.publicMethod = function () {
			document.getElementById("publicMethodCall").innerHTML = "Hi, I am called from publicMethod";
		}
		
	}
	ns.myCreator = myCreator;
}(window.privateAndPublic))

Here you can see how private method is declared:

function privateMethod

and public method:

self.publicMethod

When you open console and check what newly created object has, you will see that there is no privateMethod (because it is inaccessible):

Example download from here.