使用尾递归实现javascript函数

const myArray = [
  { id: 'root' },
  { id: 0, parent: 'root' },
  { id: 1, parent: 'root' },
  { id: 2, parent: 0 },
  { id: 3, parent: 1 },
  { id: 4, parent: 2 },
  { id: 5, parent: 1 },
  { id: 6, parent: 4 },
  { id: 7, parent: 0 },
  { id: 8, parent: 0 },
];


function makeNestedTreeFromArray(array, id, children) {
  if (children.length <= 0) {
    return array.find(entry => entry.id === id);
  }
  return ({
    ...array.find(entry => entry.id === id),
    children: children.map(child => makeNestedTreeFromArray(
      array,
      child.id,
      array.filter(entry => entry.parent === child.id),
    ))
  });
}

const myTree = makeNestedTreeFromArray(
  myArray,
  'root',
  myArray.filter(entry => entry.parent === 'root'),
);

console.log(myTree);

function getTree(data, root, index = 0, tree = {}) {
    var o = data[index];
    if (!o) return tree[root];
    Object.assign(tree[o.id] = tree[o.id] || {}, o);
    tree[o.parent] = tree[o.parent] || {};
    tree[o.parent].children = tree[o.parent].children || [];
    tree[o.parent].children.push(tree[o.id]);
    return getTree(data, root, index + 1, tree);
}

const
    data = [{ id: 'root' }, { id: 0, parent: 'root' }, { id: 1, parent: 'root' }, { id: 2, parent: 0 }, { id: 3, parent: 1 }, { id: 4, parent: 2 }, { id: 5, parent: 1 }, { id: 6, parent: 4 }, { id: 7, parent: 0 }, { id: 8, parent: 0 }],
    tree = getTree(data, 'root');

console.log(tree);

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