Question

How come I can “divide” an object by a number?

Answer 1

When you execute an arithmetic operation on an object, its valueOf function is implicitly called.

Try the following to have an object that you can actually divide:

function Foo() {

    this.valueOf = function() {
        return 500;
        };

    }

var bar = new Foo();
console.log(bar/1000); // -> 0.5