Why use $ (dollar sign) in the name of javascript variables? [duplicate]

This question already has answers here: Closed 12 years ago.

Possible Duplicates:

Why would a javascript variable start with a dollar sign?

JQuery : What is the difference between “var test” and “var $test”

What is the difference between this two ways of initializing variables?

var $val = 'something'

     OR

var val = 'something'

as I see they are the same thing.

Maybe in this case $ is only the part of name in variable? (it will become 开发者_运维百科a meaningless question in that case:/)

Thanks

---

The $ in the variable name is only part of the name, but the convention is to use it to start variable names when the variable represents a jQuery object.

var $myHeaderDiv = $('#header');
var myHeaderDiv = document.getElementById('header');

Now later in your code, you know the $myHeaderDiv is already a jQuery object, so you can call jQuery functions:

$myHeaderDiv.fade();

To get from the DOM-variable to the jQuery variable:

var $myHeaderDiv = jQuery(myHeaderDiv); //assign to another variable
jQuery(myHeaderDiv).fade(); //use directly

//or, as the $ is aliased to the jQuery object if you don't specify otherwise:
var $myHeaderDiv = jQuery(myHeaderDiv); //assign
$(myHeaderDiv).fade(); //use

To get from the jQuery variable to the DOM-variable.

var myHeaderDiv = $myHeaderDiv.get(0);

---

You are correct. $ is a part of the name of the variable.
This is not perl or PHP :)

---

No real difference..

It is usally used to signify a variable holding a jquery or other javascript framework object, because they can have shorthand $ function..

It is just easier to identify the type of the contents..

---

There are 28 letters in the alphabet as far as JavaScript is concerned. a-z, _ and $. Anywhere you can use a letter in JavaScript you can use $ as that letter. (<c> Fellgall @ http://www.webdeveloper.com/forum/showthread.php?t=186546)

In your example $val and val will be two different variable names.

---

syom - in my case, i use the $ prefix to indicate that it's a variable that is referenced by jquery. It's purely a part of the variable and not a reserved character.

keeps it easy to identify in long code runs..

jim