bainary-tree-traversal.js

class TreeNode {
  constructor(value) {
    this.value = value;
    this.left = null;
    this.right = null;
  }
}

class BainaryTree {
  constructor(root) {
    this.root = root;
  }

  preOrderTraversal(node) {
    if (node == null) {
      return [];
    }

    let result = [node.value];
    result = result.concat(this.preOrderTraversal(node.left));
    result = result.concat(this.preOrderTraversal(node.right));

    return result;
  }
  inOrderTraversal(node) {
    if (node == null) {
        return [];
      }
  
      let result = [];
      result = result.concat(this.inOrderTraversal(node.left));
      result.push(node.value);
      result = result.concat(this.inOrderTraversal(node.right));
  
      return result;
  }

  postOrderTraversal(node) {
    if (node == null) {
        return [];
      }
  
      let result = [];
      result = result.concat(this.postOrderTraversal(node.left));
      result = result.concat(this.postOrderTraversal(node.right));
      result.push(node.value);
  
      return result;
  }
}

const node = new TreeNode(1);
node.left = new TreeNode(2);
node.left.left = new TreeNode(2);
node.left.right = new TreeNode(11);
node.right = new TreeNode(3);
node.right.right = new TreeNode(3);
const tree = new BainaryTree(node);

console.log(tree.preOrderTraversal(tree.root));
console.log(tree.inOrderTraversal(tree.root));
console.log(tree.postOrderTraversal(tree.root));