tree.js

function Node(data) {
  this.data = data;
  this.children = [];
}

class Tree {
  constructor() {
    this.root = null;
  }

  add(data, toNodeData) {
    const node = new Node(data);
    const parent = toNodeData ? this.findBFS(toNodeData) : null;

    if (parent) parent.children.push(node);
    else if (!this.root) this.root = node;
    else return "Root already exists!";
  }

  findBFS(data) {
      const queue= [this.root]
      let _node = null

      this.traverseBFS(node => {
          if(Node.data == data)
            _node = node
      })

      return _node;
  }

  traverseBFS(cb) {
      const queue = [this.root]

      if(cb)
        while(queue.length){
            const node = queue.shift()

            cb(node)

            for(const child of node.children)
                queue.push(child)
        }
  }
}


(function test(){
    let tree = new Tree();

    tree.add("Node1")
    tree.add("Node2", "Node1")
    tree.add("Node3", "Node1")
    tree.add("Node4", "Node2")
    tree.add("Node5", "Node3")

    tree.traverseBFS(node => console.log("Current Node: ", node))
})()