jondavidjohn jondavidjohn - 3 months ago 9
Javascript Question

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

While reviewing some of the code written in the Twitter Bootstrap Javascript, it looks like they're calling immediately invoked anonymous functions like this:

!function( $ ) {

...

}(window.jQuery || window.ender);


Where I've traditionally seen this same thing accomplished this way:

(function($) {

...

})(window.jQuery || window.ender);


The first way seems a bit hacky, and I'm not sure if there is any benefit or reason for doing it this way rather than the second way? Note that I understand how it works, I'm looking to understand why they chose that way to do it.

Answer
  • One less character when minified.
  • The ! should handle where other JavaScript code is concatenated before this and doesn't have a trailing semi-colon.

There is not a huge difference. I would use whatever you were more comfortable with. You should probably toss something at the start of your example to avoid...

base.js

var lol = function() {
   alert(arguments[0]);
}

im-concat-to-base.js

(function() {
    // Irrelevant.
})();

jsFiddle.

Toss in a leading ; and she works...

jsFiddle.

...or a ! like the Twitter Bootstrap...

jsFiddle.