Seeding the random number generator in Javascript

Question

Is it possible to seed the random number generator (Math.random) in Javascript?

Answer 1

Antti Sykäri's algorithm is nice and short. I initially made a variation that replaced JavaScript's Math.random when you call Math.seed(s), but then Jason commented that returning the function would be better:

Math.seed = function(s) {
    return function() {
        s = Math.sin(s) * 10000; return s - Math.floor(s);
    };
};

// usage:
var random1 = Math.seed(42);
var random2 = Math.seed(random1());
Math.random = Math.seed(random2());

This gives you another functionality that JavaScript doesn't have: multiple independent random generators. That is especially important if you want to have multiple repeatable simulations running at the same time.