[Algorithm] 4 week(1.30 ~ 2.6) 1/3

1748. Sum of Unique Elements

  const map = new Map();
  
  for (let i of nums) {
    if (map.has(i)) map.set(i, map.get(i) + 1);
    else map.set(i, 1);
  }
  
  return [...map].reduce((acc, curr) => curr[1] === 1 ? acc + curr[0] : acc, 0);