CODEWITHSUNDEEP
javascript
Billy Moon
Billy Moon

Reputation: 58601

Unknown javascript function declaration pattern

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

Upvotes: 0

Views: 76

Answers (2)

Parv Sharma
Parv Sharma

Reputation: 12705

lets decode it step by step

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

//the outer brackets removed now as u can see a function is defined which is a normal way to define a function
which takes one argument def
immediately after the definition there is a bracket
so if we breakit down further then

function(def) //function 1
    {
        if(typeof module!='undefined'){
            module.exports=def;
        }
        else{
            this.nut=def;
        }
    }( function() /*function 2*/{}());

this simply means that second function is passed as a parameter to the first function
a bracket () just after the definition of a function in JS signifies that that function here function 1 will be call immediately after the definition. and what ever is inside the brackets will be passed to the function as parameter so def basically is function2

Upvotes: 1

jackwanders
jackwanders

Reputation: 16040

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/

Upvotes: 2

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