19-12-20_isHappy.js

/**
 * @param {number} n
 * @return {boolean}
 */
var isHappy = function(n) {
  function getSum(n){
      let sum = 0;
      for(let i = 0; i < n.toString().length; i++ ){
          sum += n.toString()[i]**2;
      }
      return sum;
  }
  while(n !== 1){
      if([4,16,37,58,89,145,42,20].indexOf(n) !== -1) break;
      n = getSum(n)
  }
  
  return n === 1 ? true : false;
};