How does JavaScript implement the drag-and-sort function of page elements?

JavaScript How to implement the drag and sort function of page elements?

In modern web development, drag sorting is a very common feature, which allows users to change their position on the page by dragging elements. This article will introduce how to use JavaScript to implement the drag-and-sort function of page elements and provide specific code examples.

The basic idea of ​​​​implementing the drag sorting function is as follows:

1. First, create elements that require drag sorting in HTML, such as a set of divs.

   <div class="sortable">元素1</div>
   <div class="sortable">元素2</div>
   <div class="sortable">元素3</div>
   <div class="sortable">元素4</div>

2. Use CSS to make these elements draggable:

   .sortable {
     cursor: grab;
   }

3. Bind an event listener for each draggable element , monitor the drag start, drag process and drag end events:

   const sortables = document.querySelectorAll('.sortable');
   let draggingElement = null;
   
   sortables.forEach(sortable => {
     sortable.addEventListener('dragstart', dragStart);
     sortable.addEventListener('dragover', dragOver);
     sortable.addEventListener('dragend', dragEnd);
   });

4. Save the dragged element in the drag start event and set the drag effect:

   function dragStart(e) {
     draggingElement = this;
     this.classList.add('dragging');
     e.dataTransfer.effectAllowed = 'move';
     e.dataTransfer.setData('text/html', this.innerHTML);
   }

5. Prevent the default behavior in the drag process event and set the drag effect:

   function dragOver(e) {
     e.preventDefault();
     this.classList.add('dragover');
     e.dataTransfer.dropEffect = 'move';
   }

6. Update the element position in the drag end event and Remove drag-related styles:

   function dragEnd(e) {
     this.classList.remove('dragging', 'dragover');
   
     const dropzone = document.querySelector('.dragover');
     if (dropzone && dropzone !== this) {
    const parentNode = this.parentNode;
    parentNode.insertBefore(this, dropzone.nextSibling);
     }
   
     draggingElement = null;
   }

With the above code, we can implement a simple drag-and-sort function for page elements. When the user drags an element, other elements automatically adjust their positions, allowing the elements to be reordered.

In the above example, we used the HTML5 drag and drop API to implement the drag sorting function. The drag-and-drop API includes a series of drag-and-drop-related events and methods that help us handle dragging and dropping operations on elements.

It should be noted that the code in the above example simply implements the drag sorting function. In actual applications, some special circumstances may need to be considered, such as sorting a large number of elements, sorting nested elements, etc. . In addition, due to differences in compatibility of drag and drop APIs in different browsers, developers may need to perform compatibility processing.

In summary, JavaScript can implement the drag-and-sort function of page elements through the drag-and-drop API. Hope the above examples are helpful to you!

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