Node: Generate 6 digits random number using crypto.randomBytes

Question

What is the correct way to generate exact value from 0 to 999999 randomly since 1000000 is not a power of 2?

This is my approa

Answer 1

I call it the random_6d algo. Worst case just a single additional loop.

var random_6d = function(n2){
    var n1 = crypto.randomBytes(3).readUIntLE(0, 3) >>> 4;

    if(n1 < 1000000)
        return n1;

    if(typeof n2 === 'undefined')
        return random_6d(n1);

    return Math.abs(n1 - n2);
};

loop version:

var random_6d = function(){
    var n1, n2;

    while(true){
        n1 = crypto.randomBytes(3).readUIntLE(0, 3) >>> 4;

        if(n1 < 1000000)
            return n1;

        if(typeof n2 === 'undefined')
            n2 = n1;
        else
            return Math.abs(n1 - n2);
    };
};