web3-keccak256.js

var answerHash = '0xdb81b4d58595fbbbb592d3661a34cdca14d7ab379441400cbfa1b78bc447c365';

// iterate through all possible uint8
for (var i = 0; i < 2 ** 8; i++) {
  var hex = i.toString(16);
  var padUint8 = web3.padLeft(hex, 2);
  var hash = web3.sha3(padUint8, {encoding: 'hex'});
  if (hash == answerHash) {
    console.log(`Found: ${i}`);
    break;
  }
}

// compare keccak256 hash
// pad to uint8
console.log('uint8:   ' + web3.sha3(web3.padLeft((170).toString(16), 2),  {encoding: 'hex'}));
// pad to uint (uint256)
console.log('uint256: ' + web3.sha3(web3.padLeft((170).toString(16), 64), {encoding: 'hex'}));