Question

I was looking at Twitter’s embedded code and saw that they are using !function. While I know that this evaluates to false, I was wondering what the point of it was.

Here is the code I am referring to:

!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");

Answer 1

It’s to save a byte. It’s the shortest way to invoke the function. The alternative would have been:

(function(){...})();

Note the syntax Twitter uses:

!function(){...}(params);

Which means that they have decreased the length to invoke a function by one byte.

EDIT: Just an after thought: It also makes it very clear that you are invoking the anonymous function.