In JavaScript, is there a way to inherit from the Number function?

Question

So I know I can do this...

Number.prototype.square = function () { return this * this }
 [Function]
4..square()
 16

Is there a way to inherit f

Answer 1

Yes, you can easily inherit from the Number.prototype. The trick is to make your objects convertible to numbers by giving them a .valueOf method:

function NumLib(n) {
    if (!(this instanceof NumLib)) return new NumLib(n);
    this.valueOf = function() {
        return n;
    }
}
NumLib.prototype = Object.create(Number.prototype);
NumLib.prototype.square = function () { return this * this }

The cast will happen whenever a mathematical operation is applied to the object, see also this answer. The native Number methods don't really like to be called on derived objects, though.