How to generate random hex string in javascript

Question

How to generate a random string containing only hex characters (0123456789abcdef) of a given length?

Answer 1

Short alternative using spread operator and .map()

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Demo 1

const genRanHex = size => [...Array(size)].map(() => Math.floor(Math.random() * 16).toString(16)).join('');

console.log(genRanHex(6));
console.log(genRanHex(12));
console.log(genRanHex(3));

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1. Pass in a number (size) for the length of the returned string.

2. Define an empty array (result) and an array of strings in the range of [0-9] and [a-f] (hexRef).

3. On each iteration of a for loop, generate a random number 0 to 15 and use it as the index of the value from the array of strings from step 2 (hexRef) -- then push() the value to the empty array from step 2 (result).

4. Return the array (result) as a join('')ed string.

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Demo 2

const getRanHex = size => {
  let result = [];
  let hexRef = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];

  for (let n = 0; n < size; n++) {
    result.push(hexRef[Math.floor(Math.random() * 16)]);
  }
  return result.join('');
}

console.log(getRanHex(6));
console.log(getRanHex(12));
console.log(getRanHex(3));

Answer 2

NodeJS Users

You can use randomBytes available in the crypto module, to generate cryptographically strong pseudorandom data of a given size. And you can easily convert it to hex.

import crypto from "crypto";

const randomString = crypto.randomBytes(8).toString("hex");

console.log(randomString)  // ee48d32e6c724c4d

The above code snippet generates a random 8-bytes hex number, you can manipulate the length as you wish.