Question

我的数据有以下属性：

每个条目都有唯一的ID（Id）
每个都有一个父字段，它指向父母的ID。
一个节点可以有多个子节点，但只有一个父节点。

我第一次尝试建造一棵树。它是错误的，因为递归导致无限循环。即使我解决了，我也不确定是否有更好的方法来做到这一点。目前，我正在进行2次传球。

我希望它尽可能高效，因为我有相当数量的数据。它还需要动态重建树（根可以是任何节点）

以下程序中有样本数据：

 arry = [{"Id":"1", "Name":"abc", "Parent":""}, {"Id":"2", "Name":"abc", "Parent":"1"},
    {"Id":"3", "Name":"abc", "Parent":"2"},{"Id":"4", "Name":"abc", "Parent":"2"}]//for testing

我希望输出是（它可能是错误的嵌套结构，因为我手动编写它。但是，我希望是一个有效的JSON结构，其中节点作为字段'值'而子节点作为数组。）

{
 "value": {"Id":"1", "Name":"abc", "Parent":""},
 "children": [
  {
   "value": {"Id":"2", "Name":"abc", "Parent":"1"},
   "children": [
    {
     "value": {"Id":"3", "Name":"abc", "Parent":"2"},
     "children": []
     },
     {
     "value": {"Id":"4", "Name":"abc", "Parent":"2"},
     "children": []
     }
   ]
..
}

示例程序：

function convertToHierarchy(arry, root) 
{
//root can be treated a special case, as the id is known
    arry = [{"Id":"1", "Name":"abc", "Parent":""}, {"Id":"2", "Name":"abc", "Parent":"1"},
    {"Id":"3", "Name":"abc", "Parent":"2"},{"Id":"4", "Name":"abc", "Parent":"2"}]//for testing


    var mapping = {}; // parent : [children]
    for (var i = 0; i < array.length; i++) 
    {
        var node = arry[i];

    if (!mapping[node.Id]) { 
          mapping[node.Id] = {value: node, children:[] } ;
        }else{
      mapping[node.Id] = {value: node} //children is already set    
    }

    if (!mapping[node.Parent]) { //TODO what if parent doesn't exist.
                mapping[node.Parent] =  {value: undefined, children:[ {value: node,children:[]} ]};
        }else {//parent is already in the list
        mapping[node.Parent].children.push({value: node,children:[]} )
    }

    }
    //by now we will have an index with all nodes and their children.

    //Now, recursively add children for root element.

    var root = mapping[1]  //hardcoded for testing, but a function argument
    recurse(root, root, mapping)
    console.log(root)

    //json dump
}

function recurse(root, node, mapping)
{
    var nodeChildren = mapping[node.value.Id].children;
    root.children.push({value:node.value, children:nodeChildren})
   for (var i = 0; i < nodeChildren.length; i++) {
        recurse(root, nodeChildren[i], mapping);
    }
    return root;
}

到目前为止，我有3个很好的解决方案，并希望这些赞成能提出更具惯用性和高效率的实施方案。我不确定，利用我的数据的属性，输入数组中只有一个根元素，并且总是给出根，这些实现中的任何一个都可能更好。我也应该学习如何进行基准测试，因为我的要求是如何有效地（快速/没有太多内存）树可以重建。例如，输入已经缓存（数组）并重建树，如

convertToHierarchy(parentid)
....
convertToHierarchy(parentid2)
...

Answer 1

这是一个解决方案：

var items = [
    {"Id": "1", "Name": "abc", "Parent": "2"},
    {"Id": "2", "Name": "abc", "Parent": ""},
    {"Id": "3", "Name": "abc", "Parent": "5"},
    {"Id": "4", "Name": "abc", "Parent": "2"},
    {"Id": "5", "Name": "abc", "Parent": ""},
    {"Id": "6", "Name": "abc", "Parent": "2"},
    {"Id": "7", "Name": "abc", "Parent": "6"},
    {"Id": "8", "Name": "abc", "Parent": "6"}
];

function buildHierarchy(arry) {

    var roots = [], children = {};

    // find the top level nodes and hash the children based on parent
    for (var i = 0, len = arry.length; i < len; ++i) {
        var item = arry[i],
            p = item.Parent,
            target = !p ? roots : (children[p] || (children[p] = []));

        target.push({ value: item });
    }

    // function to recursively build the tree
    var findChildren = function(parent) {
        if (children[parent.value.Id]) {
            parent.children = children[parent.value.Id];
            for (var i = 0, len = parent.children.length; i < len; ++i) {
                findChildren(parent.children[i]);
            }
        }
    };

    // enumerate through to handle the case where there are multiple roots
    for (var i = 0, len = roots.length; i < len; ++i) {
        findChildren(roots[i]);
    }

    return roots;
}

console.log(buildHierarchy(items));

Answer 2

这是另一个。这适用于多个根节点：

function convertToHierarchy() { 

    var arry = [{ "Id": "1", "Name": "abc", "Parent": "" }, 
    { "Id": "2", "Name": "abc", "Parent": "1" },
    { "Id": "3", "Name": "abc", "Parent": "2" },
    { "Id": "4", "Name": "abc", "Parent": "2"}];

    var nodeObjects = createStructure(arry);

    for (var i = nodeObjects.length - 1; i >= 0; i--) {
        var currentNode = nodeObjects[i];

        //Skip over root node.
        if (currentNode.value.Parent == "") {
            continue;
        }

        var parent = getParent(currentNode, nodeObjects);

        if (parent == null) {
            continue;
        }

        parent.children.push(currentNode);
        nodeObjects.splice(i, 1);
    }

    //What remains in nodeObjects will be the root nodes.
    return nodeObjects;
}

function createStructure(nodes) {
    var objects = [];

    for (var i = 0; i < nodes.length; i++) {
        objects.push({ value: nodes[i], children: [] });
    }

    return objects;
}

function getParent(child, nodes) {
    var parent = null;

    for (var i = 0; i < nodes.length; i++) {
        if (nodes[i].value.Id == child.value.Parent) {
            return nodes[i];
        }
    }

    return parent;
}

Answer 3

我做过这样的事情。它处理多个根节点，并且相当可读IMO。

array = [{"Id":"1", "Name":"abc", "Parent":""}, 
    {"Id":"2", "Name":"abc", "Parent":"1"},
    {"Id":"3", "Name":"abc", "Parent":"2"},
    {"Id":"4", "Name":"abc", "Parent":"2"},
    {"Id":"5", "Name":"abc", "Parent":""},
    {"Id":"6", "Name":"abc", "Parent":"5"}];


function buildHierarchy(source)
{

    Array.prototype.insertChildAtId = function (strId, objChild)
    {
        // Beware, here there be recursion
        found = false;
        for (var i = 0; i < this.length ; i++)
        {
            if (this[i].value.Id == strId)
            {
                // Insert children
                this[i].children.push(objChild);
                return true;
            }
            else if (this[i].children)
            {
                // Has children, recurse!
                found = this[i].children.insertChildAtId(strId, objChild);
                if (found) return true;
            }
        }
        return false;
    };

    // Build the array according to requirements (object in value key, always has children array)
    var target = [];
    for (var i = 0 ; i < array.length ; i++)
        target.push ({ "value": source[i], "children": []});

    i = 0;
    while (target.length>i)
    {
        if (target[i].value.Parent)
        {
            // Call recursion to search for parent id
            target.insertChildAtId(target[i].value.Parent, target[i]); 
            // Remove node from array (it's already been inserted at the proper place)
            target.splice(i, 1); 
        }
        else
        {
            // Just skip over root nodes, they're no fun
            i++; 
        }
    }
    return target;
}

console.log(buildHierarchy(array));

Answer 4

上述解决方案确实有效-我认为它们非常慢，并且没有太多的循环和过时的方法进行了优化（我们将使用 ES6 >语法）。我建议使用经过优化的波纹管解决方案，这将为您带来性能上的提升。 Read this blog post to understand how this works.

javascript

const hierarchy = (data) => {
    const tree = [];
    const childOf = {};
    data.forEach((item) => {
        const { Id, Parent } = item;
        childOf[Id] = childOf[Id] || [];
        item.children = childOf[Id];
        Parent ? (childOf[Parent] = childOf[Parent] || []).push(item) : tree.push(item);
    });
    return tree;
};

// print
console.log(hierarchy([{"Id":"1", "Name":"abc", "Parent":""}, {"Id":"2", "Name":"abc", "Parent":"1"}, {"Id":"3", "Name":"abc", "Parent":"2"},{"Id":"4", "Name":"abc", "Parent":"2"}], { idKey: 'Id', parentKey: 'Parent' }));

以下是一些结果以及其他海报之间的比较

http://jsben.ch/ekTls

如果您正在寻找带有动态性更高但速度稍慢的版本的参数版本，则如下所示：

const hierarchy = (data = [], { idKey = 'id', parentKey = 'parentId', childrenKey = 'children' } = {}) => {
    const tree = [];
    const childrenOf = {};
    data.forEach((item) => {
        const { [idKey]: id, [parentKey]: parentId = 0 } = item;
        childrenOf[id] = childrenOf[id] || [];
        item[childrenKey] = childrenOf[id];
        parentId ? (childrenOf[parentId] = childrenOf[parentId] || []).push(item) : tree.push(item);
    });
    return tree;
}

骇客入侵

Answer 5

在ES6中实现，带有简单的示例输入。可以在浏览器控制台中测试

let array = [{ id: 'a', children: ['b', 'c'] }, { id: 'b', children: [] }, { id: 'c', children: ['b', 'd'] }, { id: 'd', children: ['b'] }],
  tree = (data) => {
      let nodes = Object.create(null),
          result = {};
      data.forEach((item) => {
        if (!nodes[item.id]) {
          nodes[item.id] = {id: item.id, children: []}
          result = nodes
        }
        item.children.forEach((child) => {
          nodes[child] = {id: child, children: []}
          nodes[item.id].children.push(nodes[child])
        })
      })
      return result
    }

console.log(tree(array))

Answer 6

请问如果我在nodejs中使用它并且需要创建嵌套的ul / li而不是json怎么办？可以写代码

Javascript：构建分层树

6 个答案: