Courtesy Steven Robinson, simple example with inline docs. The outer function is the closure, and even after it returns, everything within it is still available in memory.

gistfile1.txt

<script type="text/javascript">

// define a var to be used as an app namespace
var APP = (function () {

  // define an object which will be returned, single 'var' pattern
	var app = {},

		// define some private 'functions' and vars if necessary
		priv1 = function () {
			console.log('priv1');
		},

		priv2 = function () {
			console.log('priv2');
		},

		priv3 = function () {
			console.log('priv3');
		};

	// assign any functions you want to become public to the app var
	app.method1 = priv3;

	// return the app var
	return app;

}());// this is a self invoking immediate function, when the page loads (script runs), APP will get the return value immediately (Object app)

// outside of the self invoking function, APP === Object app, returned from the outer function
APP.method1();	// logs 'priv3'
APP.priv1();	// logs 'Uncaught TypeError', function is private (but could be called from within priv3 and still accessible in APP)

</script>