// 字符串里面找到第k个唯一出现1次的字符串 function print(str, k) { const obj = {} for (let i = 0; i < str.length; i++) { if (!obj[str[i]]) { obj[str[i]] = 1 } else { obj[str[i]]++ } } const res = [] for (const p in obj) { if (obj[p] === 1) { res.push(p) } } return res.splice(k - 1, 1) } console.log(print('aaabbbsxxp', 2));//x