添加77. 组合优化JavaScript版本

Author: flames519

problems/0077.组合优化.md

@@ -147,7 +147,7 @@ public:
 
 
 Java：
-```
+```java
 class Solution {
     List<List<Integer>> result = new ArrayList<>();
     LinkedList<Integer> path = new LinkedList<>();
@@ -220,6 +220,28 @@ func backtrack(n,k,start int,track []int){
 }
 ```
 
+javaScript:
+
+```js
+var combine = function(n, k) {
+    const res = [], path = [];
+    backtracking(n, k, 1);
+    return res;
+    function backtracking (n, k, i){
+        const len = path.length;
+        if(len === k) {
+            res.push(Array.from(path));
+            return;
+        }
+        for(let a = i; a <= n + len - k + 1; a++) {
+            path.push(a);
+            backtracking(n, k, a + 1);
+            path.pop();
+        }
+    }
+};
+```
+