treee.js

/* Setup */
class Node {
  left = null;
  right = null;
  constructor(val) {
    this.val = val;
  }
}

const A = new Node('A');
const B = new Node('B');
const C = new Node('C');
const D = new Node('D');
const E = new Node('E');
const F = new Node('F');
const G = new Node('G');
const H = new Node('H');

A.left = B;
A.right = C;

B.left = D;
B.right = E;
C.left = F;
C.right = G;

G.right = H;
// ==============


/* Tree */
// BFS:- 
// iteratively
function bfsIter(node) {
  const queue = [];
  stack.push(node); //FIFO

  while(stack.length) {
    let curr = stack.shift();
    console.log(curr.val);
    if (curr.left) stack.push(curr.left);
    if (curr.right) stack.push(curr.right);
  }
}

// recursive
function bfsRec(node) {

  bfs([node]);
  function bfs(queue) {
    if (!queue.length) return;
    let curr = queue.shift();
    console.log(curr.val);
    if (curr.left) queue.push(curr.left);
    if (curr.right) queue.push(curr.right);
    bfs(queue);
  }
}


// DFS:- 
// recursive
// https://www.geeksforgeeks.org/tree-traversals-inorder-preorder-and-postorder/

// Preorder (Root, Left, Right) : 1 2 4 5 3
function dfsRecPre(node) {
  if (!node) return;

  console.log(node.val);
  dfsRecPre(node.left);
  dfsRecPre(node.right);
}

// Inorder (Left, Root, Right) : 4 2 5 1 3
function dfsRecIn(node) {
  if (!node) return;

  dfsRecIn(node.left);
  console.log(node.val);
  dfsRecIn(node.right);
}

// Postorder (Left, Right, Root) : 4 5 2 3 1
function dfsRecPost(node) {
  if (!node) return;

  dfsRecPost(node.left);
  dfsRecPost(node.right);
  console.log(node.val);
}

// iterative
function dfsItrPre() {
  
}

function dfsItrIn() {

}

function dfsItrPost() {

}