Katbin

function TreeNode(value) {
  this.value = value;
  this.children = [];
  this.parent = null;

  this.setParentNode = function (node) {
    this.parent = node;
  };

  this.getParentNode = function () {
    return this.parent;
  };

  this.addNode = function (node) {
    node.setParentNode(this);
    this.children[this.children.length] = node;
  };

  this.getChildren = function () {
    return this.children;
  };

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

const root = new TreeNode(1);
root.addNode(new TreeNode(2));
root.addNode(new TreeNode(3));

const children = root.getChildren();
for (let i = 0; i < children.length; i++) {
  for (let j = 0; j < 5; j++) {
    children[i].addNode(new TreeNode("second level child " + j));
  }
}

console.log(root);
children[0].removeChildren();
console.log(root);
console.log(root.getParentNode());
console.log(children[1].getParentNode());