There are about million questions like this, but each and every answer I saw just uses Math.random() (and in the rare case where someone has managed to use crypto.getRandomValues(), it's incredibly biased), but I need something that's cryptographically secure. I'm looking especially something like Python's secrets.randbelow(). Even better if there's a counterpart to secrets.choice(). Is there anything like that available in the standard Javascript without jQuery or other insanely large and complex dependencies? I couldn't find anything from Mozilla's documentation either.
Or should I just implement it myself? Would something like the following work or is there something I have completely missed?
//Return a random int in the range [0, n).
function randbelow(n) {
if (n < 1) {
throw 'Upper bound must be positive.';
}
if (n === 1) {
return 0;
}
const maxsize = 2 ** 32;
if (n > maxsize) {
throw 'Only unsigned 32-bit integers are supported.';
}
const rem = maxsize % n;
const limit = maxsize - rem;
let r;
do {
r = crypto.getRandomValues(new Uint32Array(1))[0];
} while (r >= limit);
return r % n;
}
// test
var arr = ['item1', 'item2', 'item3'];
console.log(arr[randbelow(arr.length)]);
TLDR;
import { randomInt } from 'https://cdn.jsdelivr.net/npm/random-browser';
console.log('Random number chosen from (0, 1, 2): ' + randomInt(3));
Since every "answer" on this site basically boiled down to one of the following:
Math.random().I wrote couple of functions that mimic crypto module from Node.js and borrow ideas from Python's secrets module. The whole thing is around one kilobyte without any other dependencies. I still find it kinda crazy that in 2022 JavaScript doesn't offer any way to natively generate cryptographically random integers.
<script type="module">
import { choice, randomBits, randomBytes, randomInt, tokenHex } from 'https://cdn.jsdelivr.net/npm/random-browser';
console.log('Pick a random fruit from array: ' + choice(['Apple', 'Banana', 'Orange']));
console.log('Pick a random character from string: ' + choice('ABCDEF'));
console.log('Random integer with 4 random bits (<16): ' + randomBits(4));
console.log('3 random bytes e.g. [218, 82, 127]: ' + randomBytes(3));
console.log('Random number chosen from (0, 1, 2): ' + randomInt(3));
console.log('The dice rolled: ' + randomInt(1, 7));
console.log('32 character hexadecimal string from 16 random bytes: ' + tokenHex(16));
</script>