Random Binary in JavaScript/Node.JS

Question

I am trying to find the fastest way of generating a random binary string of a certain length. As in, a certain number of random booleans.

Here's my current code - is there a much faster way?

function getRandomBits(n){
    var generator = crypto.pseudoRandomBytes;
    var generated = "";
    while(generated.length < n){
        var randomBytes = generator(4).readUInt32BE(0, true).toString(2);
        //Remove first byte as this is always one and so not random
        randomBytes = randomBytes.substring(1, randomBytes.length - 1);
        if(n - generated.length > randomBytes.length) generated = generated + randomBytes;
        else generated = generated + randomBytes.substring(0, n - generated.length);
    }
    console.log(generated);
    return generated;
}

Thanks!

Answer 1

It is unclear what "random booleans" means.

Just get the number of byte you need without going through an integer conversion.

From the node.js documentation:

const buf = crypto.randomBytes(256);

The crypto.randomBytes() method will block until there is sufficient entropy. This should normally never take longer than a few milliseconds. The only time when generating the random bytes may conceivably block for a longer period of time is right after boot, when the whole system is still low on entropy.

If you need some other form just post-process the bytes, each bit is essentially random.

Note: Although the function is named getRandomBits(n) it seems to be actually getting n bytes, not n bits.