An example of how closures work, and what makes them special

closure.js

/**
 * We are not assigning a function to myObject, only the result of
 * invoking a function. While the returned object (which is assigned
 * to "myObject") contains methods that can access the "value" variable,
 * the "value" variable cannot be accessed directly through "myObject".
 * This is how closures achieve information hiding, a.k.a. private variables.
 *
 * Information hiding is useful when we want to provide users with an interface,
 * and prevent users from tampering with the javascript objects in ways that we
 * do not want them to (hacking with private vars).
 */

var myObject = (function () {
    var value = 0;

    return {
        increment: function (inc) {
            value += typeof inc === 'number' ? inc : 1;
        },
        getValue: function () {
            return value;
        }
    };
}());