JavaScript - Advantages of object literals

Question

I've read that rather than simply writing a bunch of functions, I should use an object literal.

What are the advantages of object literal, with examples?

Answer 1

As Russ Cam said, you avoid polluting the global namespace, which is very important in these days of combining scripts from multiple locations (TinyMCE, etc.).

As Alex Sexton said, it makes for good code organisation as well.

If you're using this technique, I'd suggest using the module pattern. This still uses object literals, but as the return value from a scoping function:

var MyThingy = (function() {

    function doSomethingCool() {
        ...
    }

    function internalSomething() {
        ....
    }

    function anotherNiftyThing() {
        // Note that within the scoping function, functions can
        // call each other direct.
        doSomethingCool();
        internalSomething();
    }

    return {
        doSomethingCool: doSomethingCool,
        anotherNiftyThing: anotherNiftyThing
    };
})();

External use:

MyThingy.doSomethingCool();

The scoping function is wrapped around all of your functions, and then you call it immediately and store its return value. Advantages:

• Functions are declared normally and therefore have names. (Whereas with the {name: function() { ... }} format, all of your functions are anonymous, even though the properties referencing them have names.) Names help tools help you, from showing call stacks in a debugger, to telling you what function threw an exception. (2015 Update: The latest JavaScript specification, ECMAScript 6th edition, defines a large number of ways the JavaScript engine must infer a function's name. One of those is when the function is assigned to a property as in our {name: function() { ... }} example. So as engines implement ES6, this reason will go away.)
• Gives you the freedom of having private functions only used by your module (such as my internalSomething above). No other code on the page can call those functions; they're truly private. Only the ones you export at the end, in the return statement, are visible outside the scoping function.
• Makes it easy to return different functions depending on environment, if the implementation just changes completely (such as IE-vs-W3C stuff, or SVG vs. Canvas, etc.).

Example of returning different functions:

var MyUtils = (function() {
    function hookViaAttach(element, eventName, handler) {
        element.attachEvent('on' + eventName, handler);
    }

    function hookViaListener(element, eventName, handler) {
        element.addEventListener(eventName, handler, false);
    }

    return {
        hook: window.attachEvent ? hookViaAttach : hookViaListener
    };
})();

MyUtils.hook(document.getElementById('foo'), 'click', /* handler goes here */);

Answer 2

Using an object literal (a.k.a. object literal pattern) will not pollute the global namespace as severely as using many functions declared globally will, and also helps to organise code in a logical fashion

For example, this object literal

var obj = {
              find : function(elem) { /* find code */ },
              doSomething: function() { /* doSomething code */ },
              doSomethingElse: function() { /* doSomethingElse code */ }
          }

compared to

function find(elem) { /* find code */ },
function doSomething() { /* doSomething code */ },
function doSomethingElse() { /* doSomethingElse code */ }

will create only one property on the global object compared to three. You can then easily use the functions like so

obj.doSomething();

Answer 3

Rebecca Murphey did a talk on Object Literals at this year's jQuery Conference. One of the best reasons to use them is simply good code organization.

Here is Rebecca's write up on the Object Literal Pattern : http://rmurphey.com/blog/2009/10/15/using-objects-to-organize-your-code/

Answer 4

I’ve always used object literals because they are a clear way to organise code. Which is why I don't like prototype; it's too messy.

Functions don't pollute the name space as someone mentioned in previous answers any more than object literals.

You could easily write a literal like

var obj = {}
var find = function(elem) { /* Find code */ },
var doSomething = function() { /* doSomething code */ },
var doSomethingElse = function() { /* doSomethingElse code */ }

Which would pollute by creating lots of global objects, the same as the functions. Similarly you could do:

(function() {
    function find(elem) { /* Find code */ },
    function doSomething() { /* doSomething code */ },
    function doSomethingElse() { /* doSomethingElse code */ }
})();

Which would not create those global objects (everything is an object in JavaScript).

that way you still don't create loads of global objects.

To my mind object literals have two advantages. One they are used by many plugins such as jQuery so people are familier and they are easy to read. Making them easy to pass through data into a plugin. It's easy to create both public and private methods....

They can be slow though as every time you create an instance of the object all it's methods are duplicated. It's my understanding that that isn't the case with prototype as you have one copy of the methods and new ojects simply reference the prototype.

I could be wrong of course...