How to add nodes to tree in react

How to add nodes to the tree in react: 1. Introduce antd's tree control and implement tree-shaped components through "const treeData = [...]"; 2. Pass the key value of the current node , and then traverse the data array; 3. When traversing the array to add nodes, just add nodes through the query algorithm of nested array objects.

The operating environment of this tutorial: Windows 10 system, react18.0.0 version, Dell G3 computer.

How to add nodes to the tree in react?

The React project introduces antd's tree control to implement node addition, deletion and modification

Preface

When browsing some mainstream interview questions, I found that some interview questions asked me to write the addition, deletion and modification functions of a tree control based on antd. I originally thought that it was a component of antd. It should be pretty simple, but I didn’t expect that it took a lot of effort when I started doing it. So I plan to record the entire process of realizing the requirements.

1. Introducing antd's tree control

Everyone who has used antd should know that to use antd is to paste its code example, and then use it according to your own requirements and the API provided by antd. So here I am also looking for a simple antd tree control code example, no matter what, paste it in first and see what the result is.

import React from "react";
import { Tree } from "antd";const treeData = [
  {
    title: "0-0",
    key: "0-0",
    children: [
      {
        title: "0-0-0",
        key: "0-0-0",
        children: [
          { title: "0-0-0-0", key: "0-0-0-0" },
          { title: "0-0-0-1", key: "0-0-0-1" },
          { title: "0-0-0-2", key: "0-0-0-2" },
        ],
      },
      {
        title: "0-0-1",
        key: "0-0-1",
        children: [
          { title: "0-0-1-0", key: "0-0-1-0" },
          { title: "0-0-1-1", key: "0-0-1-1" },
          { title: "0-0-1-2", key: "0-0-1-2" },
        ],
      },
      {
        title: "0-0-2",
        key: "0-0-2",
      },
    ],
  },
  {
    title: "0-1",
    key: "0-1",
    children: [
      { title: "0-1-0-0", key: "0-1-0-0" },
      { title: "0-1-0-1", key: "0-1-0-1" },
      { title: "0-1-0-2", key: "0-1-0-2" },
    ],
  },
  {
    title: "0-2",
    key: "0-2",
  },];export default function TreeDemo() {
  return (
    <div>
      <tree></tree>
    </div>
  );}

A simple tree-shaped component is implemented here, but this component has basically no function except for browsing, so it needs to be reshaped.

2. Transform the component code structure

Generally when using antd components, the most important thing is to use the API provided by antd. Although we do not You know how to write it, but it should be pretty easy if you know how to use it. When browsing the API of the tree control, I found that the <tree></tree> component has a sub-component <treenode></treenode>, which is the smallest unit that makes up the entire tree control. So if we want to implement additions, deletions and modifications, we must work hard on this <treenode></treenode> component. Based on this idea, it is then transformed into the following.

import React, { useState } from "react";import { Tree } from "antd";const { TreeNode } = Tree;const treeData = [
  {
    value: "0",
    key: "0",
    children: [
      {
        value: "0-1",
        key: "0-1",
      },
      {
        value: "0-2",
        key: "0-2",
      },
    ],
  },];export default function TreeDemo() {
  const [data, setdata] = useState(treeData);
  const renderTreeNodes = (data) => {
    let nodeArr = data.map((item) => {
      item.title = <span>{item.value}</span>;

      if (item.children) {
        return (
          <treenode>
            {renderTreeNodes(item.children)}
          </treenode>
        );
      }

      return <treenode></treenode>;
    });

    return nodeArr;
  };

  return (
    <div>
      <tree>{renderTreeNodes(data)}</tree>
    </div>
  );}

Then it looks like the following:

The point to note here is that the title of <treenode></treenode> receives ReactNode type data, so You can use this to define your own style for displaying data, such as adding icons and the like. Then at this point, everyone should know that the requirements say that there should be addition, deletion and modification functions. You can use this title to show it. The victory is right in front of you, and then you can transform the code.

import React, { useState } from "react";import { Tree } from "antd";import {
    EditOutlined,
    PlusOutlined,
    MinusOutlined,
  } from "@ant-design/icons";const { TreeNode } = Tree;const treeData = [
  {
    value: "0",
    key: "0",
    children: [
      {
        value: "0-1",
        key: "0-1",
      },
      {
        value: "0-2",
        key: "0-2",
      },
    ],
  },];export default function TreeDemo() {
  const [data, setdata] = useState(treeData);
  const renderTreeNodes = (data) => {
    let nodeArr = data.map((item) => {
      item.title = (
        <div>
          <span>{item.value}</span>
          <span>
            <editoutlined></editoutlined>

            <plusoutlined></plusoutlined>
           
            <minusoutlined></minusoutlined>
          </span>
        </div>
      );

      if (item.children) {
        return (
          <treenode>
            {renderTreeNodes(item.children)}
          </treenode>
        );
      }

      return <treenode></treenode>;
    });

    return nodeArr;
  };

  return (
    <div>
      <tree>{renderTreeNodes(data)}</tree>
    </div>
  );}

Now there are three buttons, but the specific functions are still not available, so let’s do them one by one.

3. Implement the function of adding nodes

To add nodes, the method is to pass the key value of the current node and then traverse the data array. When traversing the array to add nodes, it involves the query algorithm of nested array objects, which uses the depth-first and breadth-first traversal ideas of arrays learned in the previous two weeks.
The following is the code modified based on this idea:

import React, { useState } from "react";import { Tree } from "antd";import { EditOutlined, PlusOutlined, MinusOutlined } from "@ant-design/icons";const { TreeNode } = Tree;const treeData = [
  {
    value: "0",
    key: "0",
    children: [
      {
        value: "0-1",
        key: "0-1",
      },
      {
        value: "0-2",
        key: "0-2",
      },
    ],
  },];export default function TreeDemo() {
  const [data, setdata] = useState(treeData);

  const renderTreeNodes = (data) => {
    let nodeArr = data.map((item) => {
      item.title = (
        <div>
          <span>{item.value}</span>
          <span>
            <editoutlined></editoutlined>

            <plusoutlined>onAdd(item.key)} />

            <minusoutlined></minusoutlined>
          </plusoutlined></span>
        </div>
      );

      if (item.children) {
        return (
          <treenode>
            {renderTreeNodes(item.children)}
          </treenode>
        );
      }

      return <treenode></treenode>;
    });

    return nodeArr;
  };

  const onAdd = (key) => {
    addNode(key,treeData); 
    //useState里数据务必为immutable （不可赋值的对象），所以必须加上slice()返回一个新的数组对象
    setdata(treeData.slice())
  };

  const addNode = (key,data) =>
    data.forEach((item) => {
      if (item.key === key) {
        if (item.children) {
          item.children.push({
            value: "default",
            key: key + Math.random(100), // 这个 key 应该是唯一的
          });
        } else {
          item.children = [];
          item.children.push({
            value: "default",
            key: key + Math.random(100),
          });
        }
        return;
      }
      if (item.children) {
       addNode(key, item.children);
      }
    });

  return (
    <div>
      <tree>{renderTreeNodes(data)}</tree>
    </div>
  );}

Click the Add button to appear a new default node:

3. Implementation Edit node function

With the idea of ​​adding nodes above, the subsequent editing and deletion functions will be easier to do. Only code snippets are shown here, and the final version of the code is at the end of the article. When editing a node, you need to make the node editable, so you need to use a variable to manage it.

  const onEdit = (key) => {
    editNode(key, treeData);
    setData(treeData.slice())
  };

  const editNode = (key, data) =>
    data.forEach((item) => {
      if (item.key === key) {
        item.isEditable = true;
      } else {
        item.isEditable = false;
      }
      item.value = item.defaultValue; // 当某节点处于编辑状态，并改变数据，点击编辑其他节点时，此节点变成不可编辑状态，value 需要回退到 defaultvalue
      if (item.children) {
        editNode(key, item.children);
      }
    });const treeData = [
  {
    value: "0",
    key: "0",
    isEditable: false,
    children: [
      {
        value: "0-1",
        key: "0-1",
        isEditable: false,
      },
      {
        value: "0-2",
        key: "0-2",
        isEditable: false,
      },
    ],
  },];

4. Implement the delete node function

 const onDelete = (key) => {
    deleteNode(key, treeData);
    setData(treeData.slice());
  };

  const deleteNode = (key, data) =>
    data.forEach((item, index) => {
      if (item.key === key) {
        data.splice(index, 1);
        return;
      } else {
        if (item.children) {
          deleteNode(key, item.children);
        }
      }
    });

5. Complete code

import React, { useState} from "react";import { Tree } from "antd";import {
  EditOutlined,
  PlusOutlined,
  MinusOutlined,
  CloseOutlined,
  CheckOutlined,} from "@ant-design/icons";import {nanoid} from "nanoid";const { TreeNode } = Tree;const treeData = [
  {
    value: "0",
    defaultValue: "0",
    key: "0",
    parentKey: '0',
    isEditable: false,
    children: [
      {
        value: "0-1",
        key: "0-1",
        defaultValue: "0-1",
        isEditable: false,
      },
      {
        value: "0-2",
        key: "0-2",
        defaultValue: "0-2",
        isEditable: false,
      },
    ],
  },];const expandedKeyArr = ["0"];export default function TreeDemo() {
  const [data, setData] = useState(treeData);
  const [expandedKeys, setExpandedKeys] = useState(expandedKeyArr);

  const onExpand = (expandedKeys) => {
    //记录折叠的key值
    setExpandedKeys(expandedKeys);
  };
  const renderTreeNodes = (data) => {
    let nodeArr = data.map((item) => {
      if (item.isEditable) {
        item.title = (
          

             onChange(e, item.key)} />

             onClose(item.key, item.defaultValue)}
            />

             onSave(item.key)}
            />
          

        );
      } else {
        item.title = (
          

            {item.value}
            
               onEdit(item.key)}
              />

               onAdd(item.key)}
              />
              {item.parentKey === "0" ? null : (
                 onDelete(item.key)}
                />
              )}
            
          
        );
      }

      if (item.children) {
        return (
          
            {renderTreeNodes(item.children)}
          
        );
      }

      return <treenode></treenode>;
    });

    return nodeArr;
  };

  const onAdd = (key) => {
    if (expandedKeys.indexOf(key) === -1) {
      expandedKeyArr.push(key);
    }
    setExpandedKeys(expandedKeyArr.slice());

    addNode(key, treeData);
    //useState里数据务必为immutable （不可赋值的对象），所以必须加上slice()返回一个新的数组对象
    setData(treeData.slice());
  };

  const onEdit = (key) => {
    editNode(key, treeData);
    setData(treeData.slice());
  };

  const editNode = (key, data) =>
    data.forEach((item) => {
      if (item.key === key) {
        item.isEditable = true;
      } else {
        item.isEditable = false;
      }
      item.value = item.defaultValue; // 当某节点处于编辑状态，并改变数据，点击编辑其他节点时，此节点变成不可编辑状态，value 需要回退到 defaultvalue
      if (item.children) {
        editNode(key, item.children);
      }
    });

  const addNode = (key, data) =>
    data.forEach((item) => {
      if (item.key === key) {
        if (item.children) {
          item.children.push({
            value: "default",
            key: nanoid(), // 这个 key 应该是唯一的
          });
        } else {
          item.children = [];
          item.children.push({
            value: "default",
            key: nanoid(),
          });
        }
        return;
      }
      if (item.children) {
        addNode(key, item.children);
      }
    });

  const onChange = (e, key) => {
    changeNode(key, e.target.value, treeData);
    setData(treeData.slice());
  };

  const changeNode = (key, value, data) =>
    data.forEach((item) => {
      if (item.key === key) {
        item.value = value;
      }
      if (item.children) {
        changeNode(key, value, item.children);
      }
    });

  const onSave = (key) => {
    saveNode(key, treeData);
    setData(treeData.slice());
  };

  const saveNode = (key, data) =>
    data.forEach((item) => {
      if (item.key === key) {
        item.defaultValue = item.value;
      }
      if (item.children) {
        saveNode(key, item.children);
      }
      item.isEditable = false;
    });

  const onClose = (key, defaultValue) => {
    closeNode(key, defaultValue, treeData);
    setData(treeData);
  };

  const closeNode = (key, defaultValue, data) =>
    data.forEach((item) => {
      item.isEditable = false;
      if (item.key === key) {
        item.value = defaultValue;
      }
      if (item.children) {
        closeNode(key, defaultValue, item.children);
      }
    });

  const onDelete = (key) => {
    deleteNode(key, treeData);
    setData(treeData.slice());
  };

  const deleteNode = (key, data) =>
    data.forEach((item, index) => {
      if (item.key === key) {
        data.splice(index, 1);
        return;
      } else {
        if (item.children) {
          deleteNode(key, item.children);
        }
      }
    });

  return (
    

      
        {renderTreeNodes(data)}
      
    
  );}

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