202. 快乐数

/**
 * @param {number} n
 * @return {boolean}
 */
var isHappy = function (n) {
  const cache = new Map()
  let sum = n
  const cal = (num) => {
    let arr = [...(num + '')]
    let sum = arr.reduce((pre, cur) => pre + cur ** 2, 0)
    return sum
  }
  while (sum !== 1) {
    sum = cal(sum)
    if (cache.has(sum)) {
      return false
    } else {
      cache.set(sum, true)
    }
  }
  return true
}