Depth First Search with Post Order Traversal in JavaScript

dfs-post-order.js

class Node {
  constructor(data) {
    this.data = data;
    this.children = [];
  }
  add(data) {
    this.children.push(new Node(data));
  }
  remove(data) {
    this.children = this.children.filter(child => child.data !== data);
  }
}

class Tree {
  constructor() {
    this.root = null;
  }
  // DFS with Post Order traversal
  traverseDFPost(fn) {
    let arr = [this.root];
    let result = [];
    while (arr.length) {
      const node = arr.pop();
      result.unshift(node);
      arr.push(...node.children);
    }
    while (result.length) {
      const node = result.shift();
      fn(node);
    }
  }
}
const lettersPostOrder = [];
const t1 = new Tree();
t1.root = new Node(20);
t1.root.add(15);
t1.root.add(30);
t1.root.children[0].add(10);
t1.root.children[0].add(18);
t1.root.children[1].add(40);

t1.traverseDFPost(node => {
  lettersPostOrder.push(node.data);
});
console.log(lettersPostOrder); // This will print [10, 18, 15, 40, 30, 20]