Generate secure random string values in Javascript using cryto-random bytes

random_hash.js

/** Generate secure random string values in Javascript using cryto-random bytes */
function randomHash (len) {
    return Array.from(
        window.crypto.getRandomValues(new Uint8Array(Math.ceil(len / 2))),
        (b) => ("0" + (b & 0xFF).toString(16)).slice(-2)
    ).join("")
}

// Simple tests with various lengths

let n = 4
while (true) {
    console.log("%s: %s", n, randomHash(n))
    if (n === 256) break
    n = n * 2
}

//   4: 156c
//   8: cce7c574
//  16: 26e5cb8a5d17e467
//  32: c9872b2cc69f01f0cb9b60141d9e23ea
//  64: 5b8b83dfab5462a36876c0726ec0ae77bec797ad97f7b220d1b8e90e5c46aa29
// 128: c5d78f8d129ea77660e27647473c2dc45f334d17e597e35add293b80a42e28e08c2596f2bb0ca07fc84139ecb0a5522dc8c79028fd3e3bfdfc8253cc2e41682b
// 256: 18350b6954beb9a606d716418aa1d9584aead14f381d5fa0c770f5a0c413ab28f3c0c4c6f428bc17e72183574977b129495c399ec82249fb477390eec89693c537018131e88b39a97df33713a5f87940ff01fcd03f09f4a125f4918b7481847ffdafe0f8a04fb63910ce58db92d667bd6cb4c8e42af19be4480e89c8c67c38ad