merge object array via discriminator - append only

merge.js

function merge(dest, src, discriminator) {
  if (!discriminator) {
    return [...dest, ...src];
  }
  const result = [...dest];
  src.forEach((s) => {
    const match = dest.find(d => d[discriminator] === s[discriminator]);
    if (match) {
      const oldVal = JSON.stringify(match);
      const newVal = JSON.stringify(s);
      if (oldVal !== newVal) {
        const index = result.indexOf(match);
        result[index] = s;
        return;
      }
      return;
    }
    result.push(s);
  });
  return result;
}