Question

I’m getting different values for i by calling add function differently. Could someone explain what’s happening here?

var i = 0;
var add = function() {
    ++i;
    return function() {
        i++;
        return function() {
            i++;
            add();
        }
    }
 };
add(); // i = 1;
add()(); // i = 2;        
add()()(); // i = 4;

​

Answer 1

The function add returns a function. And this function returns another function.

So :

add(); // Executes add, which returns a function.
add()(); // Execute the function returned by add.
add()()(); // Execute the function returned by the function returned by add

Each function just adds 1 to the i value. That explains the i value.