This question already has answers here:
JavaScript plus sign in front of function expression
(4 answers)
Closed 5 years ago.
I had look at this question to know about what this means.
(function($) {
})(jQuery);
I am looking at different bootstrap plugins, which have +function ($), while defining the function.
What does + does here, does it appends this function to other functions ?
To guide the javascript parser, that the thing written near the unary operator + is an expression.
EDIT: You can create javascript functions anonymously. This is one of the syntaxes to create the same. By doing so, when they are called (i.e evaluated), they act like a returning a function value. You can read more from the second link which provides a good description of it.
This link explains it well
Once declared, if not named, these can be executed inline like IIFE (Immediately invoked function expressions) as well. And in this form, they can then be used to create plugins or used as namespaces and attached to window object or jquery object for use later.
Good sample file to see anonymous function code in action
http://www.programering.com/a/MTMwITMwATk.html
It's a bang function
the + operator is faster than usual !
see more at
javascript function leading bang ! syntax
Related
This question already has answers here:
Explain the encapsulated anonymous function syntax
(10 answers)
Closed 6 years ago.
Lets assume we have
function () {}.bind(null);
and
(function () {}).bind(null);
Why the first one doesn't work in developer console (it throws syntax error) but both of them work in code (".js" file in website).
I think its because you are trying to define an anonymous function. Console has no future way of referencing it so its a pointless endeavour, youre defining a function you have no way of calling. If you define it as a variable it works:
var a = function () {}.bind(null);
Also I dont think its binding related. Defining an anonymous function without binding and you have the same error
Edits
A statement that begins with the keyword "function" must be a valid
function declaration statement. That requires a name for the function.
In an expression (or expression statement), that rule is different; no
name is necessary because the function acts as a value in that
context. No name is required then.
via #Pointy from this answer
A function declaration cannot be anonymous, but a function expression
can. A stand alone anonymous function looks like a function
declaration that is missing an identifier to JavaScript. But, combined
with an operator, JavaScript treats an anonymous function as the
operator's operand expression.
via #gilly3 from this answer
This question already has answers here:
Reason behind this self invoking anonymous function variant
(5 answers)
Closed 8 years ago.
I just took a look at the underscore.js source code and when i strip the source code down to its bare containing IIFE it looks like this:
(function() {
}.call(this));
I always used the syntax with outer parantheses (function() {}).call(this); and wondered if this syntax is also valid and common?
If you're asking about the location of the outer ) specifically, then whether it's located immediately after the closing brace or after the entire expression doesn't matter for the most part. Either way doesn't make a difference to how the IIFE is executed.
The only difference here is the .call(this), which is invoked as a member of the function expression — a typical IIFE has just the inner parentheses immediately following the closing brace. The reason .call(this) is used is detailed in a number of other answers including this one.
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.