🌳 Understanding Trees in JavaScript with Simple Traversals

When learning Data Structures and Algorithms (DSA), trees are one of the most interesting and useful structures. In this blog, we’ll explore what a tree is, how to create one in JavaScript, and how to traverse it using different techniques.

Let’s dive into the basics with some code!

🌱 What is a Tree?

A tree is a non-linear data structure where each element (called a node) is connected in a hierarchical manner. Each node has:

• A piece of data.

• A left child.

• A right child.

In our example, we’ll focus on a binary tree, where each node has at most two children.

🛠️ Step 1: Creating the Tree Structure

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

Here, TreeNode is a class to create each node. Every node holds data, and optionally a left and right child node.

🌳 Step 2: Building the Tree

const root = new TreeNode('R');
const nodeA = new TreeNode('A');
const nodeB = new TreeNode('B');
const nodeC = new TreeNode('C');
const nodeD = new TreeNode('D');

// Linking the nodes
root.left = nodeA;
root.right = nodeB;
nodeA.left = nodeD;
nodeB.right = nodeC;

This creates the following structure:

       R
     /   \
    A     B
   /       \
  D         C

---

🔄 Step 3: Tree Traversals Explained

Traversal means visiting each node of the tree in a particular order. We’ll cover:

🔹 1. Pre-Order Traversal (Root → Left → Right)

function preOrderTraversal(treeNode) {
    if (treeNode) {
        console.log('Node:', treeNode.data);
        preOrderTraversal(treeNode.left);
        preOrderTraversal(treeNode.right);
    }
}

Output: R → A → D → B → C

---

🔹 2. Post-Order Traversal (Left → Right → Root)

function postOderTraversal(treeNode) {
    if (treeNode) {
        postOderTraversal(treeNode.left);
        postOderTraversal(treeNode.right);
        console.log('Node:', treeNode.data);
    }
}

Output: D → A → C → B → R

---

🔹 3. In-Order Traversal (Left → Root → Right)

function inOrderTraversal(treeNode) {
    if (treeNode) {
        inOrderTraversal(treeNode.left);
        console.log('Node:', treeNode.data);
        inOrderTraversal(treeNode.right);
    }
}

Output: D → A → R → B → C

---

📌 Final Execution

console.log('🔁 Pre-Order Traversal:');
preOrderTraversal(root);

console.log('🔁 Post-Order Traversal:');
postOderTraversal(root);

console.log('🔁 In-Order Traversal:');
inOrderTraversal(root);

---

🧠 Final Thoughts

Tree structures may seem complex at first, but once you break them down into nodes and connections, they become simple and fun to play with. Using different traversal methods helps you process or search through the tree in various ways — which is powerful in real-world applications like DOM manipulation, game development, and database engines.

Stay curious, and keep coding! 🚀