trees1.js

class Node {
    constructor(value) {
        this.value = value;

        // own props for easier object shape recognition
        this.left = null;
        this.right = null;
    }
}

const traverse = (root) => {
    console.log(root.value);
    
    if (root.left != null) {
        traverse(root.left);
    }
    if(root.right != null) {
        traverse(root.right);
    }
};


/**
 * Runtime: O(n), where n is the number of nodes.
 * Solution: Print the current node. After, recursively call on the left node which will then print the left node and repeat. 
 * Once you are at the end of the tree on the left it will go to the parent node (in the previous call) and go to the right node. 
 * Then it will go up the stack until it reaches the root node and traverse the right side, starting on the left.
 * It's hard typing up the explanation...'
 **/

const first = new Node(1);
const second = new Node(2);
const third = new Node(3);
const fourth = new Node(4); 
const fifth = new Node(5);
const sixth = new Node(6);
const seventh = new Node(7);

first.left = second;
first.right = fifth;
second.left = third;
second.right = fourth;
fifth.left = sixth;
fifth.right = seventh;

traverse(first);