leetcode 剑指 Offer 50. 第一个只出现一次的字符

    1. /**
    2.  * @param {string} s
    3.  * @return {character}
    4.  */
    5. var firstUniqChar = function (s) {
    6.     let res = ' ';
    7.     let sMap = new Map();
    8.     for (let i = 0; i < s.length; i++) {
    9.         sMap.set(s[i], (sMap.get(s[i]) || 0) + 1);
    10.     }
    11.     for (let [key, item] of sMap) {
    12.         if (item == 1) {
    13.             res = key
    14.             break
    15.         }
    16.     }
    17.     return res
    18. };