add JavaScript codes for Tree

codes/javascript/chapter_tree/binary_tree_dfs.js

@@ -0,0 +1,60 @@
+/**
+ * File: binary_tree.js
+ * Created Time: 2022-12-04
+ * Author: IsChristina (christinaxia77@foxmail.com)
+ */
+
+let { arrToTree } = require("../include/TreeNode");
+
+// 初始化列表，用于存储遍历序列
+var list = []
+
+/* 前序遍历 */
+function preOrder(root){
+    if (root === null) return;
+    // 访问优先级：根结点 -> 左子树 -> 右子树
+    list.push(root.val);
+    preOrder(root.left);
+    preOrder(root.right);
+ }
+
+/* 中序遍历 */
+function inOrder(root) {
+    if (root === null) return;
+    // 访问优先级：左子树 -> 根结点 -> 右子树
+    inOrder(root.left);
+    list.push(root.val);
+    inOrder(root.right);
+}
+
+/* 后序遍历 */
+function postOrder(root) {
+    if (root === null) return;
+    // 访问优先级：左子树 -> 右子树 -> 根结点
+    postOrder(root.left);
+    postOrder(root.right);
+    list.push(root.val);
+}
+
+/* Driver Code */
+/* 初始化二叉树 */
+// 这里借助了一个从数组直接生成二叉树的函数
+var root = arrToTree([1, 2, 3, 4, 5, 6, 7, null, null, null, null, null, null, null, null]);
+console.log("\n初始化二叉树\n");
+console.log(root);
+
+/* 前序遍历 */
+list.length = 0;
+preOrder(root);
+console.log("\n前序遍历的结点打印序列 = " + list);
+
+/* 中序遍历 */
+list.length = 0;
+inOrder(root);
+console.log("\n中序遍历的结点打印序列 = " + list);
+
+/* 后序遍历 */
+list.length = 0;
+postOrder(root);
+console.log("\n后序遍历的结点打印序列 = " + list);
+