Merge pull request youngyangyang04#850 from BarneyShi/Update-Jianzhi-58-JS

剑指Offer 58 - 不使用额外空间的JS解法

Author: youngyangyang04

problems/剑指Offer58-II.左旋转字符串.md

@@ -200,17 +200,14 @@ func reverse(b []byte, left, right int){
 JavaScript：
 
 ```javascript
-var reverseLeftWords = function (s, n) {
-    const reverse = (str, left, right) => {
-        let strArr = str.split("");
-        for (; left < right; left++, right--) {
-            [strArr[left], strArr[right]] = [strArr[right], strArr[left]];
-        }
-        return strArr.join("");
-    }
-    s = reverse(s, 0, n - 1);
-    s = reverse(s, n, s.length - 1);
-    return reverse(s, 0, s.length - 1);
+var reverseLeftWords = function(s, n) {
+  const length = s.length;
+  let i = 0;
+  while (i < length - n) {
+    s = s[length - 1] + s;
+    i++;
+  }
+  return s.slice(0, length);
 };
 ```