ivanovSP

function createTree(arr, idKey, parentKey) {
  const tree = {};
  arr.forEach(n => tree[n[idKey]] = Object.assign({}, n));

  return Object.values(tree).reduce((acc, n) => {
    const parent = tree[n[parentKey]];
    (parent ? parent.children = parent.children || {} : acc)[n[idKey]] = n;
    return acc;
  }, {});
}


const tree = createTree(data, 'id', 'parent_id');