How to create a hash using Web Crypto API?

Question

I'm trying to create SHA-1 hash on the client-side. I'm trying to do this with Web Crypto API but when I'm comparing the output to what various online tools give me, the result is completely different. I think the problem is in ArrayBuffer to Hex conversion. Here is my code:

function generateHash() {
            var value = "mypassword";
            var crypto = window.crypto;
            var buffer = new ArrayBuffer(value);
            var hash_bytes = crypto.subtle.digest("SHA-1", buffer);
            hash_bytes.then(value => document.write([...new Uint8Array(value)].map(x => x.toString(16).padStart(2, '0')).join('')));
        }

Output of document.write should be:

91dfd9ddb4198affc5c194cd8ce6d338fde470e2

But it's not, I get a completely different hash of different length (should be 40). Could I have some advise on the problem? Thanks.

Answer 1

This is a basic function to generate a SHA-1 hex string digest for any input string:

async function digest(message, algo = 'SHA-1') {
  return Array.from(
    new Uint8Array(
      await crypto.subtle.digest(algo, new TextEncoder().encode(message))
    ),
    (byte) => byte.toString(16).padStart(2, '0')
  ).join('');
}