增加1382. 将二叉搜索树变平衡 JavaScript版本

problems/1382.将二叉搜索树变平衡.md

@@ -126,6 +126,29 @@ class Solution:
 Go：
 
 JavaScript：
+```javascript
+var balanceBST = function(root) {
+    const res = [];
+    // 中序遍历转成有序数组
+    const travesal = cur => {
+        if(!cur) return;
+        travesal(cur.left);
+        res.push(cur.val);
+        travesal(cur.right);
+    }
+    // 有序数组转成平衡二叉树
+    const getTree = (nums, left, right) => {
+        if(left > right) return null;
+        let mid = left + ((right - left) >> 1);
+        let root = new TreeNode(nums[mid]);// 中心位置作为当前节点的值
+        root.left = getTree(nums, left, mid - 1);// 递归地将区间[left,mid−1] 作为当前节点的左子树
+        root.right = getTree(nums, mid + 1, right);// 递归地将区间[mid+1,right] 作为当前节点的左子树
+        return root;
+    }
+    travesal(root);
+    return getTree(res, 0, res.length - 1);
+};
+```
 
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 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)