jQuery function declaration explanation

Question

I've opened jQuery 1.7.1 library and wanted to study the code, but I've found a that functions are declared in strange way (for me). For example:

show: function() {
        //some code here
},

I learned to define function on this way:

function show() {
  //some code here
}

Can someone explain me why show function is not written on second way (like in most tutorials on internet)?

Answer 1

This is because it is within an object. Object Literals have their properties defined in this way:

{
    name: value,
    //OR
    'name': value
}

Where value can be nearly anything such as a number, string, function, or even another object. In JavaScript you can also declare anonymous functions and assign them to a variable. In fact, the following declarations have the same effect:

//declares the myFunc1 function
function myFunc1() {}
//declares an anonymous function and assigns it to myFunc2
var myFunc2 = function() {};

//you can now call either like so:
myFunc1();
myFunc2();

So, combining those two concepts if I have an object and I want one of its properties to be a function I would do it like so:

var myObj = {
    name: 'My Object',
    init: function() {
        return 'Initializing!';
    },
    version: 1.0
};

alert(myObj.init());

You would then get the output: Initializing!. Make sure to check out the great documentation and tutorials on the Mozilla Developer Network, including their JavaScript Tutorial Series

Hope this helps!

Answer 2

Writing it the first way is in essence, setting a function as property of an object.

For example:

// I can create a new empty object
var myObject = {};

// or I can create a new object with a basic property
var myObject = { 
        color: "blue" 
    };

// I can also create an object with methods (like jQuery)
var myObject = { 
        color: "blue", 
        showColor: function(){ 
            alert(this.color); 
        } 
    };

// and you can use the object like this
myObject.showColor(); // calls the showColor method and will alert "blue"

This helps jQuery to encapsulate, namespace, and organize code.

Here are a couple of pretty good write-ups:

• Why do you need to invoke an anonymous function on the same line?
• http://en.wikibooks.org/wiki/JavaScript/Anonymous_Functions
• http://www.evotech.net/blog/2008/07/javascript-object-literals-a-definition/