This question already has answers here:
How does the (function() {})() construct work and why do people use it?
(15 answers)
Closed 9 years ago.
I have downloaded an external JavaScript file and want to create a HTML5 User Interface for it. I don't understand why the JavaScript code (see bellow) initiates his main function like that.
//JavaScript Code
(function(Raphael) {
// some codes here
})(window.Raphael);
Why is that function between parentheses?
What does the "window.Raphael" mean?
This is an example of a self invoking anonymous function.
You are passing in window.Raphael into this function which is essentially "renamed" to Raphael inside the function.
That is an immediately executing function (IIFE). Meaning one thats defined and executed immediately afterwards.
In this case, its also using RaphaelJS which is an SVG library. The IIFE accepts a global variable presumably defined by Raphael that is accessible at window.Raphael
Related
This question already has answers here:
What is the (function() { } )() construct in JavaScript?
(28 answers)
Closed 7 years ago.
I am learning about JavaScript functions on MDN
I came across an example that looks similar to this:
var saySomething = ( function(){console.log("hello")} )();
I have also seen this in the jQuery source.
I have not found any explanation of this style of function calling/definition on the MDN function reference.
I know from running the code that it calls itself immediately upon interpretation by the JavaScript engine.
Is this the Grouping Operator in action? Where it says:
First evaluate the body of this function and return it
Since the parentheses () immediately follow it it gets called ?
Google "Immediately Invoked Function Expression" or "IIFE".
The general syntax looks like this:
(function(){
// do something here
})():
Sometimes you'll see arguments passed in as well. It's basically used to wrap your code so none of your variables leak out into the global namespace.
This question already has answers here:
What is the purpose of a self executing function in javascript?
(21 answers)
What is the (function() { } )() construct in JavaScript?
(28 answers)
Closed 8 years ago.
I see this in some HTML files that use jQuery, at the bottom:
(function() {
setTimeout(function(){window.scrollTo(0,0);},0);
})();
What does it mean to put the whole function in round brackets?
The code you gave as example is a self-executing anonymous function.
You can read more about them here.
Relevant text from that article:
What’s useful here is that JavaScript has function level scoping. All variables and functions defined within the anonymous function aren’t available to the code outside of it, effectively using closure to seal itself from the outside world.
(function() {})(); means it is self executing anonymous function. It get called immediately when java script get rendered. More details you can search it.
setTimeout is a function which accepts two parameters:
First parameter: A function
Second parameter: an integer value in milliseconds.
By calling the setTimeout function, the function from first parameter will be called/invoked after the amount of time specified in the second parameter.
This question already has answers here:
Location of parenthesis for auto-executing anonymous JavaScript functions?
(4 answers)
Closed 9 years ago.
Is there any differences between javascript modules:
(function(){}())
vs
(function(){})()
First from book "good parts" by Crockford.
Second is code generated with Typescript.
There is no different. Also you can write the third option if your function doesn't return any value
!function(){}()
No, there is no difference between those two functions and how they're called. In both cases, you're creating an anonymous function and executing it immediately.
The only reason the "outer" parens are required is that when the JavaScript parser is expecting to see a statement, if it sees function it assumes what follows will be a function declaration. But we want to give a function expression, so by giving it an initial (, we put it into a state where it's expecting an expression.
But where the () to call the function go (after the } or outside the wrapping parens) doesn't make any difference.
No there is no difference, they both work the same. I tend to use the latter... it just seems to make more sense. (function(){}) defines the function and then you call it with (). In either case though, use a (leading)semicolon before the first (. Reference
This question already has an answer here:
Anonymous function vs normal function
(1 answer)
Closed 9 years ago.
I know this type of question gets asked a lot, but I haven't seen any question with this type of declaration
(function(){
myFuncName=function(myVar){
// some logic
};
}());
how does that differ from
function myFuncName(myVar){
// some logic
}
The first one is an anonymous function and there is no way you can reference to and call it later on, so you just executes instantly ( ) once it had been created!
(function(){
alert(1)
}())
The second one is a reference function that you can call it anytime later. It wont gets executed unless you call it explicitly
What your doing is creating an anonymous function that also has a closure in it. Read more about closures here.
Basically a closure means that you have declared a function inside of another function. Which will let you access local variables after the first function exits.
Normally you would not be able to do this since they would be out of scope.
As for the other part. You can find a very useful guide to what's happening here Why do you need to invoke an anonymous function on the same line?.
To sum it up though, you have created an anonymous self-invoking function expression.
The self-invoking comes from the fact that () immediately follows the function expression.
Here's a link which explains the the function declarations in javascript.
This question already has answers here:
Closed 12 years ago.
Possible Duplicate:
jQuery: What does (function($) {})(jQuery); mean?
I stumbled up on the following code (included in one file) but I just cannot understand what it really means.
(function ($) {
function doSomething1(somedata) {
}
function doSomething1(somedata) {
}
})(jQuery);
Question 1:
What does this syntax mean in the contex of jQuery
Question 2:
How can we call these functions let say from other files such as the HTML index file and other JavaScript files?
Thanks
This syntax is not particularly special to jquery, it's normal javascript. Here simply function
function ($) {
// some code here...
}
(note that it takes argument named $) is called with parameter jQuery (which is, obviously, global object of jQuery framework).
This is usually done when there're several js frameworks on one page (jquery, dojo, prototype, etc) which all redefine global variable $. But with this code, inside doSomething1 or doSomething2 you can always call $('.test') and be certain that call will be processed by jquery, not dojo. Because $ is not a global variable in this case, it's function parameter.
I'm not sure about your question here, but the (function() means it's self-executing,
and you call them by importing the files in the main page and then calling
doSomething1()
Mostly likely that was jQuery plugin: Plugins/Authoring