我的代码： String.prototype.delete = function (N) { var thatStr = this var max = thatStr.length if (N > max) return 0 else if (N <= 0 || N == max) return 1 else { var hash = {} for (var i = 0; i + N <= max; i++) { var sub = thatStr.slice(0, i) sub += thatStr.slice(i + N) if (!(sub in hash)) hash[sub] = 1 } return Object.keys(hash).length } } var str = 'sogou' console.log(str.delete(0)) // 1 console.log(str.delete(1)) // 5 console.log(str.delete(2)) // 3