Tady je to celý jestli to pomůže

create-a-nested-list-from-a-object

var obj = {
  items: [{
    id: 45,
    lable: "Test 1.2.1",
    parent_id: 2
  }, {
    id: 12,
    lable: "Test 1.0",
    parent_id: 0
  }, {
    id: 32,
    lable: "Test 1.1",
    parent_id: 12
  }, {
    id: 2,
    lable: "Test 1.2",
    parent_id: 12
  }]
}

var objDict = obj.items.reduce(function(p, c) {
  p[c.id] = c;
  c.children = [];
  return p;
}, {});

var tree = obj.items.reduce(function(p, c) {
  if (!c.parent_id) {
    p = c;
  } else {
    objDict[c.parent_id].children.push(c);
  }
  return p;
}, {});

processTree(tree, document.getElementById("list"));

function processTree(node, element) {
  var li = document.createElement('li');
  li.innerText = node.lable;
  element.appendChild(li);
  if (node.children.length) {
    var ul = document.createElement('ul');
    li.appendChild(ul);
    for (var i = 0; i < node.children.length; i++) {
      processTree(node.children[i], ul);
    }
  }
}