Question

I have never seen this design pattern before, what is it doing?

(function(def){
    if(typeof module!='undefined'){
        module.exports=def;
    }
    else{
        this.nut=def;
    }
}( function(){
   ...
}() ));

Answer 1

This is a “immediately invoked function expression”, as Ben Alman would say. The first function defined takes one argument, def. Wrapping this function in parantheses and passing it a second function definition (also in parentheses) immediately invokes the first function, passing it the result of the second function (it is also immediately invoked) as the def parameter.

More information: http://benalman.com/news/2010/11/immediately-invoked-function-expression/