Question

What does the following javascript code mean? I guess it’s defining a function within a function to make it look like OOP? Why the function can return multiple functions? what is the bracket at the end?

var grid_ui = function () {

    function setup_data_source() {}

    return {
        init: function () {},

        set_ds: function(rpt_headers, rpt_rows) {}
    } // return
}();

Answer 1

The { } notation is called an object literal. It is same as:

a = new Object();
a.init = function() { };
a.set_ds = function(...) { };
return a;

and return { } returns an object.

The function () { ... }(); is a self-invoking function: it creates an anonymous function them immidiately invokes it.

In your code, the self-invoking function returns an object of functions, which is a namespace pattern. The value of grid_ui now contains { init: ..., set_ds: ... }, which is mentioned in return.

These concepts are very difficult to explain in one SO answer, so I will provide you some links:

• http://www.hunlock.com/blogs/Functional_Javascript/
• http://www.dustindiaz.com/namespace-your-javascript/