242. 有效的字母异位词

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isAnagram = function(s, t) {
    return s.length === t.length ? [...s].sort().join(‘‘) == [...t].sort().join(‘‘): false;
};

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isAnagram = function(s, t) {
  if(s.length !== t.length) 
    return false;
  let sMap = new Map();
  for(let c of s){
    sMap.set(c , (sMap.get(c) ||0)+1);
  }
  for(let ch of t){
    let count = sMap.get(ch);
    if(count > 0){
      sMap.set(ch, count - 1);
    }
  }
  let res = Array.from(sMap.values()).filter((v) => v!==0);
  return res.length === 0;
};