Bcrypt with NodeJS

nodeJSbcrypt.js

const bcrypt = require('bcrypt');

let passwordHash;
bcrypt.hash('passwordString', 10, function(err, hash) {
  passwordHash = hash;
});

bcrypt.compare('differentpasswordString', passwordHash, function(err, res) {
  if(res) {
   console.log(res) //returns true
  } else {
   console.log(res) //returns false
  } 
});