添加二叉树的递归遍历javascript版本

problems/二叉树的递归遍历.md

@@ -226,7 +226,7 @@ func PreorderTraversal(root *TreeNode) (res []int) {
     var traversal func(node *TreeNode)
     traversal = func(node *TreeNode) {
 	if node == nil {
-            return
+        return
 	}
 	res = append(res,node.Val)
 	traversal(node.Left)
@@ -272,6 +272,41 @@ func PostorderTraversal(root *TreeNode) (res []int) {
 }
 ```
 
+javaScript:
+
+```js
+
+前序遍历:
+
+var preorderTraversal = function(root, res = []) {
+    if (!root) return res;
+    res.push(root.val);
+    preorderTraversal(root.left, res)
+    preorderTraversal(root.right, res)
+    return res;
+};
+
+中序遍历:
+
+var inorderTraversal = function(root, res = []) {
+    if (!root) return res;
+    inorderTraversal(root.left, res);
+    res.push(root.val);
+    inorderTraversal(root.right, res);
+    return res;
+};
+
+后序遍历:
+
+var postorderTraversal = function(root, res = []) {
+    if (!root) return res;
+    postorderTraversal(root.left, res);
+    postorderTraversal(root.right, res);
+    res.push(root.val);
+    return res;
+};
+```
+