spacetravelermemoized.js

const gridTraveler = (x, y, z, memo = new Map()) => {
  const key = `${x},${y},${z}`;
  if (memo.has(key)) return memo.get(key);
  if (x === 0 || y === 0 || z === 0) return 0;
  if (x === 1 && y === 1 && z === 1) return 1;
  memo.set(key, gridTraveler(x - 1, y, z, memo) + gridTraveler(x, y - 1, z, memo)) + gridTraveler(x, y, z - 1, memo));
  return memo.get(key);
};
console.log(gridTraveler(10, 10, 10));