This question already has answers here:
jQuery dollar sign ($) as function argument?
(4 answers)
Closed 9 years ago.
Normally when I am writing my jquery code I do something like
$(document).ready(function() {
// some code
});
I was looking at some code online and I noticed that the author did this
$(document).ready(function($) {
// some code
});
What is the use of the $ as the function parameter
jQuery calls the callback function with jQuery as the first argument. Javascript doesn't require you to define parameters that will be passed to your function so it's usually left out if it's not needed.
Here it seems weird because the author is already relying on $ being jQuery - you would normally expect it to be along the lines of:
jQuery(document).ready(function($) {
// $ works here even if someone changed the global `$`
// this breaks down if someone changed jQuery too but that's far less likely
});
The jQuery function is the value of jQuery or of $. It serves as a namespace so we can call it "The global jQuery object."
Buddy Please jquery documentation.Its well written and easy to understand . Any way i will tell you what is the $ sign. $ is a shortcut to the jQuery function. .
**$**(document).ready(function() {
// statements
});
Here $ represents jquery .You can use jquery instead of $ sign..
See this link Click here
Related
This question already has answers here:
What is the purpose of the dollar sign in JavaScript?
(12 answers)
Closed 2 years ago.
What does the $ before the function mean in Javascript? I found this in a Javascript script for a Chromium extension.
$(function() {
$('#search').change(function() {
$('#bookmarks').empty();
dumpBookmarks($('#search').val());
});
});
This looks like jQuery but could also be any number of web frameworks.
$ is simply a variable (in this case a function) name, just like any other JavaScript variable name. It likely is also available and aliased as jQuery.
You can confirm and see the version using the below in a browser's developer console while on the website.
$ === jQuery
> true
$.fn.jquery
> "1.12.1"
It means it is a function of a JQuery object, a popular javascript library
This could be an Immediately-invoked Function Expressions with jQuery. $ is equal to 'jQuery'. With the immediate function, you can define variables inside the context of the function and avoid global variable definitions. As soon as jQuery loads this function executes.
This question already has answers here:
What is the meaning of "$" sign in JavaScript
(8 answers)
Closed 8 years ago.
if you declare a function in javascript, you can't use the '$' character in the name, so how is that jquery is able to do so? For example:
function myFunction() {
$("#h01").html("Hello jQuery")
}
$(document).ready(myFunction);
but if i declare a function as so:
function $(a){
// do something
}
javascript shows an error?
From the specification,
https://es5.github.io/#x7.6
IdentifierStart ::
UnicodeLetter
$
_
\ UnicodeEscapeSequence
$ is fine as a character in the name.
Demo, using the code in the question: http://jsfiddle.net/q02go7dd/
try
var $ = function(){
// do something
};
and you won't get an error.
$ is a short-handed alias for JQuery object itself.
So when you type,
$("#h01").html("Hello jQuery");
you are calling JQuery constructor with parameter "h01".
It's like declaring a function called dave and giving it an alias ß and calling it like that.
dave("h01");
$ is fine :
$myFunction = function(){ alert("hello"); }
$myFunction(); // alerts "hello"
Jquery is a wrapper which runs over javascript. In spite of using javascript large syntax, Jquery offer small syntaxs which is easy to use.
In Jquery $ sign return Jquery object.
This question already has answers here:
What does the leading semicolon in JavaScript libraries do?
(6 answers)
What does this JavaScript/jQuery syntax mean?
(6 answers)
Closed 9 years ago.
I'm trying to understand an unusual library for controlling 3D CSS navigation. I'm reviewing the code, but I just don't understand the style.
The javascript code starts
;(function($) {
'use strict';
. . .
})(jQuery);
1) I'm really baffled by the leading semicolon, is there a reason for that?
2) I've never seen the format: (function($) { What am I looking at? Is this some sort of obtuse jquery format? I've seen lots of other formats relating to jquery.. e.g..
$(function() { // as shorthand for $( document ).ready()
but I've never seen (function($) before.. am I missing something?
3) Why is the 'use strict'; code there, if this is a jQuery code. Seems unusual.
4) Finally why is the {jQuery) code at the end of the function?
Oh, and for reference the code I'm looking at is http://www.jqueryscript.net/demo/Easy-jQuery-3D-Side-Menu-Plugin-with-CSS3-Box-Lid/
Many thanks, Zip.
1) This semicolon is here to make sure there will be no conflict when using minifiers, which adds all Javascript after each other. When combining multiple Javascript files it sometimes happens that a certain file has an error and "forgot" to end the last line with a semicolon. The semicolon makes sure the previous code line is ended.
2,4) (function($) { starts an anonymous function which is directly executed. What happens is the following. First we make an anonymous function like we always e.g.:
function($) {
}
In this function the $ is a function parameter. Now if we want to execute this function we need to enclose it in parentheses so it becomes:
(function($) {
});
Since we want to add the jQuery object as parameter for this functions we give it as a parameter like we do in every function:
(function($) {
})(jQuery);
3) Strict Mode is a new feature in ECMAScript 5 that allows you to place a program, or a function, in a "strict" operating context. This strict context prevents certain actions from being taken and throws more exceptions.
Read more information about strict mode at: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions_and_function_scope/Strict_mode and http://ejohn.org/blog/ecmascript-5-strict-mode-json-and-more/
This question already has answers here:
Immediate function invocation syntax
(3 answers)
Closed 9 years ago.
In order to use the $ symbol in jquery and not have to use jQuery.functionname, we use this
(function($) {
})(jQuery);
(In drupal, you actually have to specify this implicitly).
I don't understand this javascript syntax, why is there an initial parentheses? How is the (jQuery) at the end used?
It's just an anonymous function with an argument that's automatically invoked.
For example, if we were to expand it out a bit you'd end up with something like this:
var anon = function($) {
...
};
anon(jQuery);
The $ is a valid identifer in JavaScript and we pass in the existing jQuery object into the function for use through $, as it could be replaced later.
All that's doing is declaring an anonymous function and executing it immediately, passing in one argument (jQuery) into the function. That argument is given the name $ which can be used throughout the scope of the function.
The brackets around the function aren't strictly necessary in all contexts; see the comment under this answer for details. The gist is that they're needed here to make the function behave like an expression instead of a statement (function declaration).
This question already has answers here:
What does the exclamation mark do before the function?
(8 answers)
Closed 9 years ago.
I have been searching, but no clues... or I haven't search the proper way (so please excuse me if duplicate)
Does the following code, mean: If there is no jQuery defined, or no document ready?
!function ($) {
///
!function ($) {
$(function(){ // I know this is an alias to $(document).ready()
.....
}(window.jQuery) // Ending of !function
I'm asking, because I saw it here: http://twitter.github.io/bootstrap/assets/js/application.js and have no I really don't know what it means.
In this case, ! is being used because it's an operator, so the rest of the line will be treated as an expression rather than a statement. This is a way of writing an immediately invoked function expression. The more common idioms can be found here:
Javascript immediately invoked function patterns
! on a function(){}() simply flips (or negates) the value that's returned after immediately calling the function that's defined. Notice that immediately after the function definition, at the very last line, it says (window.jQuery) — that's passing jQuery as the argument to the function and calling it immediately.
But in this case it doesn't appear to do anything important since the return value won't be used anyway. The function will still be executed though.
Also, it says this at the top of the file:
// NOTICE!! DO NOT USE ANY OF THIS JAVASCRIPT
// IT'S ALL JUST JUNK FOR OUR DOCS!
// ++++++++++++++++++++++++++++++++++++++++++
So that's evidence further that it's not meant to serve any real purpose.