<script>
    class Node {
      constructor(key) {
        this.key = key;
        this.left = null;
        this.right = null;
      }
    }
    class CreateBinaryTree {
      constructor() {
        this.root = null;
      }
      insertNode(key) {
        // 插入节点
        if (!key) return;
        let newNode = new Node(key);
        let insert = (node, newNode) => {
          if (node.key > newNode.key) {
            if (node.left === null) {
              node.left = newNode;
            } else {
              insert(node.left, newNode);
            }
          } else {
            if (node.right === null) {
              node.right = newNode;
            } else {
              insert(node.right, newNode);
            }
          }
        }
        if (!this.root) {
          this.root = node;
        } else {
          insert(this.root, newNode);
        }
      }
      //中序遍历
      inOrder() {
        let backs = [];
        const inOrderNode = (node, callback) => {
          if (node !== null) {
            inOrderNode(node.left, callback);
            backs.push(callback(node.data));
            inOrderNode(node.right, callback)
          }
        };
        inOrderNode(this.root);
        function callback(v) {
          return v
        }
        return backs
      }
      //中序遍历
      inOrder() {
        let backs = [];
        const inOrderNode = (node, callback) => {
          if (node !== null) {
            inOrderNode(node.left, callback);
            backs.push(callback(node.data));
            inOrderNode(node.right, callback)
          }
        };
        inOrderNode(this.root);
        function callback(v) {
          return v
        }
        return backs
      }
      //前序遍历
      preOrder() {
        let backs = [];
        const preOrderNode = (node, callback) => {
          if (node !== null) {
            backs.push(callback(node.data));
            preOrderNode(node.left, callback);
            preOrderNode(node.right, callback)
          }
        };
        preOrderNode(this.root, callback);
        function callback(v) {
          return v
        }
        return backs
      }
      //后序遍历
      postOrder() {
        let backs = [];
        const postOrderNode = (node, callback) => {
          if (node !== null) {
            postOrderNode(node.left, callback);
            postOrderNode(node.right, callback);
            backs.push(callback(node.data))
          }
        };
        postOrderNode(this.root, callback);
        function callback(v) {
          return v
        }
        return bac
      }
    }
    let binaryTree = new CreateBinaryTree();
    tree.insert(11);
    tree.insert(7);
    tree.insert(5);
    tree.insert(3);
    tree.insert(9);
    tree.insert(8);
    tree.insert(10);
    tree.insert(13);
    tree.insert(12);
    tree.insert(14);
    tree.insert(20);
    tree.insert(18);
    tree.insert(25);
    console.log(tree);
  </script>

原文来自：添加链接描述 只供记录作用，如有打扰，万分抱歉