Check the equality of 2 arrays or that both contain same elements

arrayEqual.js

// compares 2 arrays
const arraysEqual = (a, b) => {
  if (a === b) return true;
  if (a == null || b == null) return false;
  if (a.length !== b.length) return false;

  // compare that both contains same elements no matter the order (optional)
  const aSort = a.sort();
  const bSort = b.sort();

  for (let i = 0; i < a.length; ++i) {
    if (aSort[i] !== bSort[i]) return false;
  }
  return true;
}