Generate a cryptographically random String with a given length

random.js

function getRandomBase64String(length) {
    var array = new Uint8Array(Math.ceil(length * 3 / 4));
    crypto.getRandomValues(array);
    return btoa(String.fromCharCode.apply(null, array)).slice(0, length);
}

function getRandomHexString(length) {
    var array = new Uint32Array(Math.ceil(length / 8));
    crypto.getRandomValues(array);
    return Array.prototype.map.call(array, i => i.toString(16).padStart(2, '0')).join('').slice(0, length);
}