deno random encoded bytes

rand.ts

import {toHashString} from 'https://deno.land/std@0.201.0/crypto/to_hash_string.ts';
import {parse} from 'https://deno.land/std@0.201.0/flags/mod.ts';

const args = parse(Deno.args, {
  boolean: ['help'],
  alias: {
    help: 'h',
    encoding: 'e',
  },
  string: ['encoding'],
  default: {
    help: false,
    encoding: 'hex',
  },
});

const help = `
Usage: deno run random.ts [options] number
Options:
  --encoding, -e  'hex' | 'base64' Default: hex
Parameters:
  number  Length of the output in bytes. Default: 32
`;

if (args.help) {
  console.log(help);
  Deno.exit(0);
}

const [num] = args._;

if (typeof num !== 'number' || isNaN(num) || num < 1 || num % 1 !== 0) {
  console.error(`Length must be a positive integer. Got: ${num}`);
  Deno.exit(1);
}

console.log(
  toHashString(
    crypto.getRandomValues(new Uint8Array(num)),
    args.encoding as 'hex' | 'base64'
  )
);
Deno.exit(0);