class Node {
  constructor(parent, id) {
    this.id = id;
    this.child = [];
    this.parent = parent;
  }

  setChild(child) {
    this.child.push(child);
  }
}

let tree = [];

const generateTree = (nodes, levels, _cLevel, _id, _cNode) => {
  if (_cLevel >= levels) return;
  if (_cLevel == null) (_cLevel = 0), (_id = 1);
  let _tNode;
  var _created = [];
  if (_cLevel == 0) {
    _cNode = new Node(null, _id);
    tree.push(_cNode);
    _created.push(_cNode);
    _tNode = _cNode;
  } else {
    const children = Math.floor(Math.random() * (nodes - 0)) + 0;
    let i = 0;
    while (i <= children) {
      _id++;
      _tNode = new Node(_cNode.id, _id);
      _cNode.setChild(_tNode.id);
      tree.push(_tNode);
      _created.push(_tNode);
      i++;
    }
  }
  _cLevel++;
  _created.forEach(element => {
    generateTree(nodes, levels, _cLevel, tree.length, element);
  });
};

generateTree(3, 4);

console.log(tree);