execution-context.js

var dog = (function () {
    // execution context: dog's module
    var nombre = "dog";

    var setName = function (newName) {
        nombre = newName;
    };

    var speak = function () {
        console.log('[' + nombre + ']: woof!');
    };

    return {
        // execution context: dog (the actually returned dog)
        setName : setName,
        speak : speak
    };
})();

dog.speak(); // [dog]: woof!
dog.setName('Shipo');
dog.speak(); // [Shipo]: woof!