Pair.js

class Node {
  constructor (val) {
    this.val = val
    this.children = []
  }
  
  addChildren (val) {
    const node = new Node(val)
    this.children.push(node)
    return node
  }
}

class Tree {
  constructor (val) {
    this.root = null
  }
  
  addNode (parent, val) {
    if (parent === null) {
      this.root = new Node(val)
      return this.root
    } 
     
    const node = this.findNode(this.root, parent)
    return node.addChildren(val)
  }
  
  findNode (current, start) {
    if (current === start) {
      return current
    }
    
    for(var index = 0; index < current.children.length; index++) {
      const node = this.findNode(current.children[index], start)
      if (node) {
        return node
      }
    }
  }
  
  // print in breath first manner
  print () {
    console.log('------')
    
    
    console.log('------')
  }
}

var tree = new Tree ()

var t1 = tree.addNode(null, 1)
var t2 = tree.addNode(t1, 2)
var t3 = tree.addNode(t1, 3)
var t4 = tree.addNode(t1, 4)

var t5 = tree.addNode(t2, 5)
var t6 = tree.addNode(t2, 6)

console.log(t1)
console.log(t2) 
console.log(t3) 
console.log(t4) 
console.log(t5) 
console.log(t6)

console.log(tree.print())