Добавить val.hierarchy в массив объектов

const arr = [
  {name: "Earth", id: 1, parent_id: -1},
  {name: "Europe", id: 2, parent_id: 1},
  {name: "America", id: 3, parent_id: 1},
  {name: "Asia", id: 4, parent_id: 1},
  {name: "New York", id: 5, parent_id: 3},
];

const items = {};
arr.forEach(item => items[item.id] = item);
const traverse = item => item ? traverse(items[item.parent_id]).concat(item.name) : [];
arr.forEach(item => item.hierarchy = traverse(item));


arr.forEach(i=>console.info(JSON.stringify(i)));

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const
    getParents = id => id in references.ids
        ? [...getParents(references.parents[id]), references.ids[id].name]
        : [],
    data = [{ name: "Earth", id: 1, parent_id: -1 }, { name: "Europe", id: 2, parent_id: 1 }, { name: "America", id: 3, parent_id: 1 }, { name: "Asia", id: 4, parent_id: 1 }],
    references = data.reduce((r, o) => {
        r.ids[o.id] = o;
        r.parents[o.id] = o.parent_id;
        return r;
    }, { ids: {}, parents: {} }),
    result = data.map(o => ({ ...o, hierarchy: getParents(o.id) }));

console.info(result);

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const arr = [
  {name: "Earth", id: 1, parent_id: -1},
  {name: "Europe", id: 2, parent_id: 1},
  {name: "America", id: 3, parent_id: 1},
  {name: "Asia", id: 4, parent_id: 1},
];

// 1. Store a mapping from ID to object for easy access
const mapping = new Map(arr.map(obj => [obj.id, obj]));

// 2. (optional) sort by ID to ensure the precondition
arr.sort((lhs, rhs) => {
  if (lhs.id == rhs.id) {
    return 0;
  }

  return lhs.id < rhs.id ? -1 : 1;
});

// 3. Build the hierarchy
arr.forEach(obj => {
  if (obj.parent_id < 0) {
    obj.hierarchy = [obj.name];
    return;
  }

  if (!mapping.has(obj.parent_id)) {
    // This is a possibility, do what you wish here
    obj.hierarchy = ["<incomplete>", obj.name];
    return;
  }

  const parent = mapping.get(obj.parent_id);
  const parentHierarchy = parent.hierarchy;
  obj.hierarchy = [...parentHierarchy, obj.name];
});

console.info(arr);