Variable declaration using $

Question

Below declaration of $. is meant to be a javascript variable ?

I understand how to use $ for selectors

$('#Text').click(function () {
  $('#Text').css('color', 'red')
});

But when I declare variable I was used to declare that as var x = function(){}...

What this notation means "$." is a jquery way of declaring variables ?

$.searchTwitter= function(){


                    $.ajax({
                        url:"http://search.twitter.com/search.json",
                        data:{
                                q:'dogs'
                        },
                        dataType:'jsonp',
                        success:function(results){
                            console.log(results);
                        }
                    });
               };

 $.searchTwitter();

Possible duplicate of [What does the $ sign mean in Jquery or JavaScript?](http://stackoverflow.com/questions/8667736/what-does-the-sign-mean-in-jquery-or-javascript) — Jeroen, Mar 20 '16 at 09:50

mmuzahid · Answer 1 · 2016-03-20T10:25:33.400

3

In jQuery, $ is an alias for jQuery.

i.e. $.ajax(); works same as jQuery.ajax();

In Javascript, $ is nothing special; just simply a valid JavaScript identifier.

Ref: https://learn.jquery.com/about-jquery/how-jquery-works/

Note: The jQuery library exposes its methods and properties via two properties of the window object called jQuery and $. $ is simply an alias for jQuery and it's often employed because it's shorter and faster to write.

edited Mar 20 '16 at 10:25

answered Mar 20 '16 at 09:51

mmuzahid

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$, Jquery is an object or a function ? – Cris Mar 20 '16 at 10:07
@Cris: In JavaScript, every function is an object and, thus, may have properties. – Callidior Mar 20 '16 at 10:10

score 2 · Answer 2 · answered Mar 20 '16 at 09:46

2

$ is jQuery itself. It's declared in the jQuery library. When you use $.searchTwitter = function(){} what you're really saying is JQuery.searchTwitter = function(){}.

answered Mar 20 '16 at 09:46

Saar Kuriel

572
4
16

score 1 · Answer 3 · answered Mar 20 '16 at 09:46

1

$ is known as Syntactic Sugar

In case of jQuery it is jQuery Object. What that means is that, using $("#mydiv") or jQuery("#mydiv") is the same. $ only eases the pain of writing the full object name jQuery.

If you want to know more

answered Mar 20 '16 at 09:46

Mihir

3,812
3
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score 1 · Answer 4 · answered Mar 20 '16 at 09:47

$ is a global variable defined by jQuery and an alias for the variable jQuery. By assigning $.searchTwitter = function() { ... } one adds a new method to the global jQuery object.

Practically, there is no advantage or disadvantage of such a declaration in contrast with the usual function searchTwitter() { ... } syntax. It is sometimes used to declare functions which are related to jQuery or are a plug-in for jQuery.

score 1 · Accepted Answer · answered Mar 20 '16 at 10:12

The dollar sign is one of the chars allowed in variable names in Javascript, along with numbers, underscores and English letters.

Examples for 'special' variable names are:

$$ $_ $ _

Dot notation is a way to assign a property to an object.

Example:

var x = { myName: 'Roman' };
x.searchTwitter = function() {}; 
x.searchTwitter();
console.log(x.myName);

When a browser loads the Jquery library, Jquery declares a global variable named Jquery and also declares an alias for it - the $.

Answer your question is no, it's not a special way of Jquery declaring variables. It's standard Javascript way of adding properties to an object.

num8er · Answer 6 · 2016-03-20T09:51:24.407

For safety reasons I like to wrap my code with closure function with $ as argument. See code below:

(function($){
  
 $.searchTwitter = function(){

    $.ajax({
      url:"http://search.twitter.com/search.json",
      data:{
        q:'dogs'
      },
      dataType:'jsonp',
      error: function (xhr, status, error) {
        $('#errors').html(JSON.stringify(xhr));
      },
      success:function(results){
        console.log(results);
        $('#results').html(JSON.stringify(results));
      }
    });
 };
 $.searchTwitter();

})(jQuery);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="results"></div><div id="errors"></div>

but Cris this Twitter API is deprecated. It should not work.

Variable declaration using $

6 Answers6