difference between $ and $() in jQuery

Question

Could someone take the effort to explain me the difference between $ and $() in jquery?

I know $() is shorthand form of $jQuery() which takes any DOM element and turns it into a jQuery object.

But what I am not sure of is what is $ and how different is it from $(). Kindly enlighten me.

Thanks heaps, Chaitanya

Answer 1

$ is a function that can be called - $().

The behaviour of $() varies immensely depending on the parameters supplied, although all examples below will return a jQuery object. It can:

1. register a document.ready handler - $(myfunc)
2. act as a selector - $('#myid')
3. construct elements - $('<div>')
4. return an empty object - $()

$ is also an object that contains various utility functions $.each, etc as properties of that object. In this context, it acts like a namespace for those functions.

Answer 2

$ = jQuery - This is the jQuery object which is used for the jQuery Utilies it contains such as $.Ajax() or $.each() Thus var j = $; will assign the jquery prototype into the variable j.

$() = jQuery() - This is a function called from the root jQuery object that is used convert DOM elements to jQuery Objects or get jQuery objects using selectors

Answer 3

Hope this helps and add on to the other posts :)

• $ = is a a valid javascript object/identifier.

• $() = calling $() creates an empty jQuery object.

jQuery() — which can also be written as $() — searches through the DOM for any elements that match the provided selector and creates a new jQuery object that references these elements:

Official Document Please read docs here (click me) I would highly recommend that you should read this document.

Your question is mix of 2 sperate questions please see below:

• What is the meaning of "$" sign in javascript

• Can someone explain what = $(); means in jQuery?

Answer 4

If i create a function:

function my_function() { alert('my_function'); return(33) }

my_function is a variable that contains a function. my_function() is the result of the function call.

You would use the function call my_function() to execute the instructions in the function and/or to get the returned result into a variable var my_var = my_function();.

You would use the variable name of the function in order to pass it to another function as a parameter such as $('a').click(my_function);

Since in JavaScript variables can be of any kind that includes scalar (literal values), arrays, objects and functions.

Now taking that idea and building on it:

$ is just a variable name just as jQuery is just a variable name.

As it so happens this variable contains a function which means that $() or jQuery() executes what ever instructions are present in the function body $.

Answer 5

$ is a reference to the jQuery namespace, via which you can access its static methods (e.g. ajax, each etc), while $() calls a function that either registers a DOM-ready callback (if a function is passed to it) or returns elements from the DOM (if a selector string or element is passed to it).

Incidentally, $ is short-hand for jQuery, not $jQuery.

Answer 6

In Javascript, everything is data, this includes function. As a contrived example:

function test() {
  console.log("test");
}

For this example, test() is the invocation of the function. Simply using test is like using a variable which allows you to do something like:

var t = test;
t();

Which then causes t to have the same data/functionality as test.

This then allows you to do something like a closure:

function closure() {
  var i = 0;
  function inner() {
    i++;
    console.log(i);
  }

  return inner;
}

Since a function is just some data, we can return it and then invoke it. So you would then write something like:

var t = closure();
t(); // prints '1'
t(); // prints '2'

Among other benefits, doing this allows you to keep your namespace a bit less cluttered.

To directly answer your question, $ is just an alias for jQuery which was made by doing:

function jQuery() { /* Lots of code */ }
$ = jQuery;