Question

Number function

> var x = new Number(5)
> x === 5
false
> Number(x) === 5
true

valueOf method

> var y = new Number(5)
> y === 5
false
> y.valueOf() === 5
true

---

Which is the preferred option? Are there benefits to using one over the other?

For the record, I’m dealing with this within a method on Number.prototype, where I can be sure that this is always a Number object.

Answer 1

I would think the valueOf is preferred, since Number conversion is meant to be used with values that are not already Number objects, but moreover – Number(x) will call valueOf method on x,
so essentially, you’d add an unnecessary sugar/overhead, where valueOf is a perfectly accepted way of receiving a primitive representation of an object (Number in your case).

As a side note:

For the record, I’m dealing with this within a method on
Number.prototype, where I can be sure that this is always a Number
object.

this is not correct as there is always a possibility that someone will do something like this:

Number.prototype.test = function()
    {
        console.log(this);
    }

var x = new Number(10);
x.test();

var foo = x.test;
foo();

would of course provide:

Number
DOMWindow

as output. It’s for you to decide whether you want to defend against it.