Johnny Johnny - 1 month ago 9
Javascript Question

What's the difference between function(){}() and !function(){}()


Possible Duplicate:

!function(){ }() vs (function(){ })()




So I was just reading through the source of the new Bootstrap (2.0) from Twitter and noticed that there is an exclamation mark before the self-invoking anonymous function. When I saw this I immediately thought "Oh crap, there's a new, better way to do this?".

See for yourself!



Anyways, what's the difference? There must be a reason for it because they use it consistently in all of their JavaScript plugins (for Bootstrap).

Another thing I noticed was the "use strict" right after this. I don't think it's related to my previous inquiry, but can anyone explain this?

Thanks!

Answer
function(){} ();

By itself (see Point's comment) isn't going to be valid, since

function() {}

is a function declaration. To invoke it immediately, you need to get the JavaScript engine to treat the function as an expression. People usually do this as either of

(function(){}) ();  //more common

(function(){} ()); // Papa Crockford's preference:

with

!function(){}();

simply being a shorthand version of the same thing.