HMAC SHA256 digest of CryptoJS does not match it of OpenSSL, so should use jsSHA instead of CryptoJS.

crypto.js

const cryptoJsHmacSHA256Digest = (key, data) => {
  const hmac = CryptoJS.HmacSHA256(data, key);
  const buffer = new ArrayBuffer(hmac.sigBytes);
  const dv = new DataView(buffer);
  hmac.words.forEach((v, i) => dv.setInt32(4*i, v, false));

  let digest = '';
  for (let i = 0; i < hmac.sigBytes; i++) {
    digest += String.fromCharCode(dv.getUint8(i));
  }
  return digest;
};

const jsShaHmacSHA256Digest = (key, data) => {
  const shaObj = new jsSHA("SHA-256", "TEXT", {
    hmacKey: { value: key, format: "BYTES" },
  });
  shaObj.update(data);
  return shaObj.getHash("BYTES");
};

const key = atob('Qs+L5/Pgxm95mtDXm78tOAAuNqjvo66e5SWwqmNoIOI=');
const data = 'data';

console.log(btoa(cryptoJsHmacSHA256Digest(key, data))); //=> mOMPodWFe0tgu3HkfnZPM6hB36NHkB7Z1fYnY/b8T3w=
console.log(btoa(   jsShaHmacSHA256Digest(key, data))); //=> 6lViS0n/FZarze0nVewa+Sjel9aeD9sbpWx/c8gvyoQ=

crypto.rb

key = Base64.dencode64('Qs+L5/Pgxm95mtDXm78tOAAuNqjvo66e5SWwqmNoIOI=')
data = 'data'
digest = OpenSSL::HMAC.digest(OpenSSL::Digest::SHA256.new, key, data)
puts Base64.encode64(digest) #=> 6lViS0n/FZarze0nVewa+Sjel9aeD9sbpWx/c8gvyoQ=