About the closure in JS

1

I am trying to finish the “Arguments Optional” challenge, my code is as below:

function addTogether() {
  if(arguments.length === 2){
    if(typeof arguments[0] !== 'number' || typeof arguments[1] !== 'number')
      return undefined;
    else
      return arguments[0] + arguments[1];
  }
  else if(arguments.length === 1){
    var c = arguments[0];
    return function(element){
       if(typeof c !== 'number' || typeof element !== 'number'){
          console.log("SSSSSSSSSSSSSSSS");
          return undefined;
       }
       else
        return element + c;
     };
  }
}

when I perform the function addTogether("http://bit.ly/IqT6zt");, the result is as below:

     function(element){
       if(typeof c !== 'number' || typeof element !== 'number'){
          console.log("SSSSSSSSSSSSSSSS");
          return undefined;
       }
       else
        return element + c;
     };

It seems that the inner function in the “addTogether” is not been performed, but as a string to be returned.

I do not know well about closure in JS, I don’t know why the inner function is not be performed.I think the result should be “undefined”.Please give me some guide.Thanks a lot!

3

Thanks for your reply!
when I make the call addTogether(“http://bit.ly/IqT6zt”), the else if check statement will run, but I still do not know why the inner anonymous function does not run? I think this is a closure in JS.

5

I solved the problem with your help, thanks a lot!