Building Deep Trees in JavaScript Using Object References

const data = [
  { id: 56, parentId: 62 },
  { id: 81, parentId: 80 },
  { id: 74, parentId: null },
  { id: 76, parentId: 80 },
  { id: 63, parentId: 62 },
  { id: 80, parentId: 86 },
  { id: 87, parentId: 86 },
  { id: 62, parentId: 74 },
  { id: 86, parentId: 74 },
];

const idMapping = data.reduce((acc, el, i) => {
  acc[el.id] = i;
  return acc;
}, {});

let root;
data.forEach(el => {
  // Handle the root element
  if (el.parentId === null) {
    root = el;
    return;
  }
  // Use our mapping to locate the parent element in our data array
  const parentEl = data[idMapping[el.parentId]];
  // Add our current el to its parent's `children` array
  parentEl.children = [...(parentEl.children || []), el];
});

{
  id: 74,
  parentId: null,
  children: [
    {
      id: 62,
      parentId: 74,
      children: [{ id: 56, parentId: 62 }, { id: 63, parentId: 62 }],
    },
    {
      id: 86,
      parentId: 74,
      children: [
        {
          id: 80,
          parentId: 86,
          children: [{ id: 81, parentId: 80 }, { id: 76, parentId: 80 }],
        },
        { id: 87, parentId: 86 },
      ],
    },
  ],
};

Источник https://dev.to/nas5w/building-deep-trees-in-javascript-using-object-references-4565