What is the difference between a dollar sign and a dollar sign followed by a period in JQuery?

Question

In jQuery, what is the difference between $ and $.? Please provide a practical explanation if possible.

Answer 1

I presume you are asking about the syntactic difference between $('#selector'); and $.parseJSON(str);.

The former is an invocation of a function called $ and the latter invokes it's method called parseJSON. Yup, functions can have methods - it is possible because Javascript functions are also objects. Figuratively speaking:

<script type="text/javascript">

function $(str) {
   alert(str);
}

$.parseJSON = function () {
   alert('Parsing JSON');
}

$('Hi');
$.parseJSON('{}');


</script>

Answer 2

From http://en.wikipedia.org/wiki/JQuery:

the $ function, which is a factory method for the jQuery object. These functions, often called commands, are chainable; they each return a jQuery object

$.-prefixed functions. These are utility functions which do not work on the jQuery object per se.

Typically, access to and manipulation of multiple DOM nodes begins with the $ function being called with a CSS selector string, which results in a jQuery object referencing matching elements in the HTML page. This node set can be manipulated by calling instance methods on the jQuery object, or on the nodes themselves. For example:

$("div.test").add("p.quote").addClass("blue").slideDown("slow");

This line finds the union of all div tags with class attribute test and all p tags with CSS class attribute quote, adds the class attribute blue to each matched element, and then slides them down with an animation. The $ and add functions affect the matched set, while the addClass and slideDown affect the referenced nodes.

The methods prefixed with $. are convenience methods or affect global properties and behaviour. For example, the following is an example of the map function called each in jQuery:

$.each([1,2,3], function(){  
document.write(this + 1); });

This writes the number 234 to the document.

Answer 3

$ is a reference (or synonym, if you want an analogy) to the global jQuery object. $.<method> calls a static method of the jQuery object, where $(<selector>) creates a new instance of the jQuery object.

Answer 4

$ - dollar sign is also same as Jquery usage. But I preferred to use dollar sign because I like the way dollar sign is.

Answer 5

In the context of jQuery, $ refers to the global jQuery object.

$. by itself is invalid JavaScript. As $ is an object, methods on this object are called like on any other object: $.methodname().

Maybe it becomes clearer by substituting $ with jQuery: jQuery.methodname().