search
HomeWeb Front-endFront-end Q&AJavaScript implements draggable tree

As Web applications are increasingly used, we increasingly need to design more efficient methods for interaction with web pages. One of them is to use JavaScript to implement a draggable tree (Drag & Drop Tree). This article will introduce how to use JavaScript to create a draggable tree, detailing the implementation process and related technical details.

1. Goals to be achieved

The draggable tree described in this article refers to a structure on the web page, which contains nodes of the tree structure, and we can drag and drop them. Reorganize their hierarchical relationships. To implement such a tree, the following two key aspects need to be completed.

  1. Implementing the tree structure

First we need to create nodes for the tree structure in the page and determine the levels and associations between the nodes. These contents can be represented using JSON. For example, we can store the structure of the tree in the following JSON format:

{
    name: "节点A",
    children: [{
        name: "子节点A1",
        children: []
    }, {
        name: "子节点A2",
        children: [{
            name: "子节点A2-1",
            children: []
        }]
    }]
}

When rendered as a tree structure, it should look like this:

- 节点A
  |- 子节点A1
  |- 子节点A2
     |- 子节点A2-1
  1. Implementing drag and drop functionality

Making nodes drag-and-drop requires the use of some JavaScript techniques. Regarding the drag and drop API, generally speaking, it involves three categories:

  • Dragable elements
  • Place target elements
  • Drag data

Using these APIs, we can easily implement the drag-and-drop function of nodes.

2. Technical details

After understanding our goals, let’s now discuss the implementation details in detail. The following are the steps to implement:

  1. Build a tree structure

We need to create node elements first and add them to HTML, usually using ul and li element levels. accomplish. For each node, a li element is required, and more li elements must be nested in the child node ul. In order to associate the tree structure with JSON data, you can use the data-* attributes to store the JSON data in the corresponding li element.

<ul id="tree">
    <li data-name="节点A">
        <div class="node">节点A</div>
        <ul>
            <li data-name="子节点A1">
                <div class="node">子节点A1</div>
            </li>
            <li data-name="子节点A2">
                <div class="node">子节点A2</div>
                <ul>
                    <li data-name="子节点A2-1">
                        <div class="node">子节点A2-1</div>
                    </li>
                </ul>
            </li>
        </ul>
    </li>
</ul>
  1. Add drag events to nodes

We need to add drag events for each node, including mousedown, dragstart, dragover, dragleave, drop and dragend. Among them, mousedown and dragstart events need to be processed before dragging starts, and subsequent processing is dragover, dragleave, drop and dragend respectively. The handling functions of these drag and drop events can be completed through event listeners.

// 获取所有节点并添加事件监听器
const nodes = document.querySelectorAll('.node');
nodes.forEach((node) => {
    node.addEventListener('mousedown', onMouseDown);
    node.addEventListener('dragstart', onDragStart);
    node.addEventListener('dragover', onDragOver);
    node.addEventListener('dragleave', onDragLeave);
    node.addEventListener('drop', onDrop);
    node.addEventListener('dragend', onDragEnd);
});
  1. Implementing the processing function of the drag event

The processing function of the drag event is somewhat complicated, and each step of the operation needs to be carefully designed. The following are instructions for each step:

  • mousedown: Record the element where the drag starts and set isDragged to true.
  • dragstart: Set the data transmission type and the data to be transmitted. In addition, it is necessary to determine whether the drag operation can be performed based on the status of isDragged. To set the data transmission type, you can use the setData() method.
function onDragStart(event) {
    if (!isDragged) {
        draggedItem = event.currentTarget.parentNode;
        event.dataTransfer.setData('text/plain', event.currentTarget.dataset.name);
        isDragged = true;
    }
}
  • dragover: Prevent the default event and add the isOver attribute to the current element. This attribute indicates that the current element is placed above other elements and can be placed. Default events can be prevented through the event.preventDefault() method.
function onDragOver(event) {
    event.preventDefault();
    if (!event.currentTarget.dataset.isOver) {
        event.currentTarget.parentNode.classList.add('over');
        event.currentTarget.dataset.isOver = true;
    }
}
  • dragleave: Remove the over attribute of the current element, indicating that there is no mouse hovering over the element.
function onDragLeave(event) {
    if (event.currentTarget.dataset.isOver) {
        event.currentTarget.parentNode.classList.remove('over');
        event.currentTarget.dataset.isOver = false;
    }
}
  • drop: Determine whether the placement operation can be performed based on whether the current element has the over attribute. If it doesn't work, exit directly; if it works, perform a placement operation and adjust the tree structure.
function onDrop(event) {
    event.preventDefault();
    if (event.currentTarget.dataset.isOver) {
        const droppedItem = event.currentTarget.parentNode;
        const parent = draggedItem.parentNode;
        parent.removeChild(draggedItem);
        event.currentTarget.parentNode.insertBefore(draggedItem, droppedItem.nextSibling);
    }
}
  • dragend: implements the termination event of drag operation. In this event, reset the value of isDragged and remove all over attributes.
function onDragEnd(event) {
    event.currentTarget.parentNode.classList.remove('over');
    event.currentTarget.dataset.isOver = false;
    isDragged = false;
}

3. Complete code

Finally, we integrate the above Javascript code to display a complete draggable tree. You can use this code directly, copy it into a text editor, save it as an html file and run it in the browser.




    
    可拖动的树
    


<ul id="tree">
    <li data-name="节点A">
        <div class="node">节点A</div>
        <ul>
            <li data-name="子节点A1">
                <div class="node">子节点A1</div>
            </li>
            <li data-name="子节点A2">
                <div class="node">子节点A2</div>
                <ul>
                    <li data-name="子节点A2-1">
                        <div class="node">子节点A2-1</div>
                    </li>
                </ul>
            </li>
        </ul>
    </li>
</ul>
<script>
    let draggedItem = null;
    let isDragged = false;

    const nodes = document.querySelectorAll('.node');
    nodes.forEach((node) => {
        node.addEventListener('mousedown', onMouseDown);
        node.addEventListener('dragstart', onDragStart);
        node.addEventListener('dragover', onDragOver);
        node.addEventListener('dragleave', onDragLeave);
        node.addEventListener('drop', onDrop);
        node.addEventListener('dragend', onDragEnd);
    });

    function onMouseDown(event) {
        event.preventDefault();
    }

    function onDragStart(event) {
        if (!isDragged) {
            draggedItem = event.currentTarget.parentNode;
            event.dataTransfer.setData('text/plain', event.currentTarget.dataset.name);
            isDragged = true;
        }
    }

    function onDragOver(event) {
        event.preventDefault();
        if (!event.currentTarget.dataset.isOver) {
            event.currentTarget.parentNode.classList.add('over');
            event.currentTarget.dataset.isOver = true;
        }
    }

    function onDragLeave(event) {
        if (event.currentTarget.dataset.isOver) {
            event.currentTarget.parentNode.classList.remove('over');
            event.currentTarget.dataset.isOver = false;
        }
    }

    function onDrop(event) {
        event.preventDefault();
        if (event.currentTarget.dataset.isOver) {
            const droppedItem = event.currentTarget.parentNode;
            const parent = draggedItem.parentNode;
            parent.removeChild(draggedItem);
            event.currentTarget.parentNode.insertBefore(draggedItem, droppedItem.nextSibling);
        }
    }

    function onDragEnd(event) {
        event.currentTarget.parentNode.classList.remove('over');
        event.currentTarget.dataset.isOver = false;
        isDragged = false;
    }
</script>

Through the above code implementation, we successfully created a draggable tree structure. In the web page, users can easily adjust the tree structure by dragging and dropping. At the same time, we also introduced in detail various technical details during the implementation process. This is undoubtedly a very useful practical case for developers who are learning JavaScript.

The above is the detailed content of JavaScript implements draggable tree. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
HTML and React's Integration: A Practical GuideHTML and React's Integration: A Practical GuideApr 21, 2025 am 12:16 AM

HTML and React can be seamlessly integrated through JSX to build an efficient user interface. 1) Embed HTML elements using JSX, 2) Optimize rendering performance using virtual DOM, 3) Manage and render HTML structures through componentization. This integration method is not only intuitive, but also improves application performance.

React and HTML: Rendering Data and Handling EventsReact and HTML: Rendering Data and Handling EventsApr 20, 2025 am 12:21 AM

React efficiently renders data through state and props, and handles user events through the synthesis event system. 1) Use useState to manage state, such as the counter example. 2) Event processing is implemented by adding functions in JSX, such as button clicks. 3) The key attribute is required to render the list, such as the TodoList component. 4) For form processing, useState and e.preventDefault(), such as Form components.

The Backend Connection: How React Interacts with ServersThe Backend Connection: How React Interacts with ServersApr 20, 2025 am 12:19 AM

React interacts with the server through HTTP requests to obtain, send, update and delete data. 1) User operation triggers events, 2) Initiate HTTP requests, 3) Process server responses, 4) Update component status and re-render.

React: Focusing on the User Interface (Frontend)React: Focusing on the User Interface (Frontend)Apr 20, 2025 am 12:18 AM

React is a JavaScript library for building user interfaces that improves efficiency through component development and virtual DOM. 1. Components and JSX: Use JSX syntax to define components to enhance code intuitiveness and quality. 2. Virtual DOM and Rendering: Optimize rendering performance through virtual DOM and diff algorithms. 3. State management and Hooks: Hooks such as useState and useEffect simplify state management and side effects handling. 4. Example of usage: From basic forms to advanced global state management, use the ContextAPI. 5. Common errors and debugging: Avoid improper state management and component update problems, and use ReactDevTools to debug. 6. Performance optimization and optimality

React's Role: Frontend or Backend? Clarifying the DistinctionReact's Role: Frontend or Backend? Clarifying the DistinctionApr 20, 2025 am 12:15 AM

Reactisafrontendlibrary,focusedonbuildinguserinterfaces.ItmanagesUIstateandupdatesefficientlyusingavirtualDOM,andinteractswithbackendservicesviaAPIsfordatahandling,butdoesnotprocessorstoredataitself.

React in the HTML: Building Interactive User InterfacesReact in the HTML: Building Interactive User InterfacesApr 20, 2025 am 12:05 AM

React can be embedded in HTML to enhance or completely rewrite traditional HTML pages. 1) The basic steps to using React include adding a root div in HTML and rendering the React component via ReactDOM.render(). 2) More advanced applications include using useState to manage state and implement complex UI interactions such as counters and to-do lists. 3) Optimization and best practices include code segmentation, lazy loading and using React.memo and useMemo to improve performance. Through these methods, developers can leverage the power of React to build dynamic and responsive user interfaces.

React: The Foundation for Modern Frontend DevelopmentReact: The Foundation for Modern Frontend DevelopmentApr 19, 2025 am 12:23 AM

React is a JavaScript library for building modern front-end applications. 1. It uses componentized and virtual DOM to optimize performance. 2. Components use JSX to define, state and attributes to manage data. 3. Hooks simplify life cycle management. 4. Use ContextAPI to manage global status. 5. Common errors require debugging status updates and life cycles. 6. Optimization techniques include Memoization, code splitting and virtual scrolling.

The Future of React: Trends and Innovations in Web DevelopmentThe Future of React: Trends and Innovations in Web DevelopmentApr 19, 2025 am 12:22 AM

React's future will focus on the ultimate in component development, performance optimization and deep integration with other technology stacks. 1) React will further simplify the creation and management of components and promote the ultimate in component development. 2) Performance optimization will become the focus, especially in large applications. 3) React will be deeply integrated with technologies such as GraphQL and TypeScript to improve the development experience.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

PhpStorm Mac version

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool

WebStorm Mac version

WebStorm Mac version

Useful JavaScript development tools