How can I make var a = add(2)(3); //5 work?

Question

I want to make this syntax possible:

var a = add(2)(3); //5

based on what I read at http://dmitry.baranovskiy.com/post/31797647

I\

Answer 1

function add(x){
  return function(y){
    return x+y
  }
}

First-class functions and closures do the job.