数组元素可以以混乱的顺序排列

let array = [ { id: 1, data: 'something', parent_id: null, children: [] }, { id: 2, data: 'something', parent_id: 1, children: [] }, { id: 5, data: 'something', parent_id: 4, children: [] }, { id: 4, data: 'something', parent_id: 3, children: [] }, { id: 3, data: 'something', parent_id: null, children: [] }, { id: 6, data: 'something', parent_id: null, children: [] } ] function buildTree(array) { let tree = [] for (let i = 0; i < array.length; i++) { if (array[i].parent_id) { let parent = array.filter(elem => elem.id === array[i].parent_id).pop() parent.children.push(array[i]) } else { tree.push(array[i]) } } return tree } const tree = buildTree(array) console.log(tree); .as-console-wrapper { min-height: 100% }

我的解决方案:

允许双向映射(根到叶，叶到根) 返回所有节点、根节点和叶节点 一次数据传递和非常快的性能 香草Javascript

/**
 * 
 * @param data items array
 * @param idKey item's id key (e.g., item.id)
 * @param parentIdKey item's key that points to parent (e.g., item.parentId)
 * @param noParentValue item's parent value when root (e.g., item.parentId === noParentValue => item is root)
 * @param bidirectional should parent reference be added
 */
function flatToTree(data, idKey, parentIdKey, noParentValue = null, bidirectional = true) {
  const nodes = {}, roots = {}, leaves = {};

  // iterate over all data items
  for (const i of data) {

    // add item as a node and possibly as a leaf
    if (nodes[i[idKey]]) { // already seen this item when child was found first
      // add all of the item's data and found children
      nodes[i[idKey]] = Object.assign(nodes[i[idKey]], i);
    } else { // never seen this item
      // add to the nodes map
      nodes[i[idKey]] = Object.assign({ $children: []}, i);
      // assume it's a leaf for now
      leaves[i[idKey]] = nodes[i[idKey]];
    }

    // put the item as a child in parent item and possibly as a root
    if (i[parentIdKey] !== noParentValue) { // item has a parent
      if (nodes[i[parentIdKey]]) { // parent already exist as a node
        // add as a child
        (nodes[i[parentIdKey]].$children || []).push( nodes[i[idKey]] );
      } else { // parent wasn't seen yet
        // add a "dummy" parent to the nodes map and put the item as its child
        nodes[i[parentIdKey]] = { $children: [ nodes[i[idKey]] ] };
      }
      if (bidirectional) {
        // link to the parent
        nodes[i[idKey]].$parent = nodes[i[parentIdKey]];
      }
      // item is definitely not a leaf
      delete leaves[i[parentIdKey]];
    } else { // this is a root item
      roots[i[idKey]] = nodes[i[idKey]];
    }
  }
  return {roots, nodes, leaves};
}

使用的例子:

const data = [{id: 2, parentId: 0}, {id: 1, parentId: 2} /*, ... */];
const { nodes, roots, leaves } = flatToTree(data, 'id', 'parentId', 0);

我已经编写了一个测试脚本来评估用户shekhardtu(见答案)和FurkanO(见答案)提出的两种最通用的解决方案的性能(意味着输入不需要事先排序，代码不依赖于第三方库)。

http://playcode.io/316025?tabs=console&script.js&output

FurkanO的解决方案似乎是最快的。

/* ** performance test for https://stackoverflow.com/questions/18017869/build-tree-array-from-flat-array-in-javascript */ // Data Set (e.g. nested comments) var comments = [{ id: 1, parent_id: null }, { id: 2, parent_id: 1 }, { id: 3, parent_id: 4 }, { id: 4, parent_id: null }, { id: 5, parent_id: 4 }]; // add some random entries let maxParentId = 10000; for (let i=6; i<=maxParentId; i++) { let randVal = Math.floor((Math.random() * maxParentId) + 1); comments.push({ id: i, parent_id: (randVal % 200 === 0 ? null : randVal) }); } // solution from user "shekhardtu" (https://stackoverflow.com/a/55241491/5135171) const nest = (items, id = null, link = 'parent_id') => items .filter(item => item[link] === id) .map(item => ({ ...item, children: nest(items, item.id) })); ; // solution from user "FurkanO" (https://stackoverflow.com/a/40732240/5135171) const createDataTree = dataset => { let hashTable = Object.create(null) dataset.forEach( aData => hashTable[aData.id] = { ...aData, children : [] } ) let dataTree = [] dataset.forEach( aData => { if( aData.parent_id ) hashTable[aData.parent_id].children.push(hashTable[aData.id]) else dataTree.push(hashTable[aData.id]) } ) return dataTree }; /* ** lets evaluate the timing for both methods */ let t0 = performance.now(); let createDataTreeResult = createDataTree(comments); let t1 = performance.now(); console.log("Call to createDataTree took " + Math.floor(t1 - t0) + " milliseconds."); t0 = performance.now(); let nestResult = nest(comments); t1 = performance.now(); console.log("Call to nest took " + Math.floor(t1 - t0) + " milliseconds."); //console.log(nestResult); //console.log(createDataTreeResult); // bad, but simple way of comparing object equality console.log(JSON.stringify(nestResult)===JSON.stringify(createDataTreeResult));

我根据@Halcyon的答案写了一个ES6版本

const array = [
  {
    id: '12',
    parentId: '0',
    text: 'one-1'
  },
  {
    id: '6',
    parentId: '12',
    text: 'one-1-6'
  },
  {
    id: '7',
    parentId: '12',
    text: 'one-1-7'
  },

  {
    id: '9',
    parentId: '0',
    text: 'one-2'
  },
  {
    id: '11',
    parentId: '9',
    text: 'one-2-11'
  }
];

// Prevent changes to the original data
const arrayCopy = array.map(item => ({ ...item }));

const listToTree = list => {
  const map = {};
  const roots = [];

  list.forEach((v, i) => {
    map[v.id] = i;
    list[i].children = [];
  });

  list.forEach(v => (v.parentId !== '0' ? list[map[v.parentId]].children.push(v) : roots.push(v)));

  return roots;
};

console.log(listToTree(arrayCopy));

该算法的原理是利用“map”建立索引关系。通过“parentId”可以很容易地在列表中找到“item”，并为每个“item”添加“children”，因为“list”是一个引用关系，所以“roots”将与整个树建立关系。

它可能是有用的包列表到树 安装:

bower install list-to-tree --save

or

npm install list-to-tree --save

例如，有列表:

var list = [
  {
    id: 1,
    parent: 0
  }, {
    id: 2,
    parent: 1
  }, {
    id: 3,
    parent: 1
  }, {
    id: 4,
    parent: 2
  }, {
    id: 5,
    parent: 2
  }, {
    id: 6,
    parent: 0
  }, {
    id: 7,
    parent: 0
  }, {
    id: 8,
    parent: 7
  }, {
    id: 9,
    parent: 8
  }, {
    id: 10,
    parent: 0
  }
];

使用包列表到树:

var ltt = new LTT(list, {
  key_id: 'id',
  key_parent: 'parent'
});
var tree = ltt.GetTree();

结果:

[{
  "id": 1,
  "parent": 0,
  "child": [
    {
      "id": 2,
      "parent": 1,
      "child": [
        {
          "id": 4,
          "parent": 2
        }, {
          "id": 5, "parent": 2
        }
      ]
    },
    {
      "id": 3,
      "parent": 1
    }
  ]
}, {
  "id": 6,
  "parent": 0
}, {
  "id": 7,
  "parent": 0,
  "child": [
    {
      "id": 8,
      "parent": 7,
      "child": [
        {
          "id": 9,
          "parent": 8
        }
      ]
    }
  ]
}, {
  "id": 10,
  "parent": 0
}];

下面是我根据上面的答案创建的一个简单的帮助函数，为通天塔环境量身定制:

import { isEmpty } from 'lodash'

export default function unflattenEntities(entities, parent = {id: null}, tree = []) {

  let children = entities.filter( entity => entity.parent_id == parent.id)

  if (!isEmpty( children )) {
    if ( parent.id == null ) {
      tree = children
    } else {
      parent['children'] = children
    }
    children.map( child => unflattenEntities( entities, child ) )
  }

  return tree

}