HTML5 Drag and Drop API is a browser natively supported drag and drop function interface. 1. It controls the drag-and-drop process through events such as dragstart, drag, dragend, dragter, dragover, drop, dragleave, etc.; 2. When implementing, draggable="true" needs to be set and event handling functions are bound, such as setting data in dragstart, and data in drop is obtained; 3. Notes include: e.preventDefault() must be called in dragover to trigger drop, dataTransfer is used to pass data, and files are processed directly through FileList when dragging files. The default behavior of some browsers needs to be blocked, and cross-domain drag-and-drop may be subject to security restrictions. This API can be used in scenarios such as file upload, list sorting, etc., but you need to pay attention to compatibility and user experience issues.

HTML5's Drag and Drop API is a set of interfaces natively provided by the browser, allowing you to easily implement the drag and drop function of elements. You don't need to rely on third-party libraries, you can do it by using JavaScript and HTML. It is suitable for file upload, list sorting, component dragging and other scenarios.

Basic process of drag and drop

Drag and drop operations are actually a process composed of several events:

• dragstart : fired when the user starts dragging an element
• drag : Continuously triggered during dragging
• dragend : Triggered when the drag ends (whether it is drop or cancel)
• dragenter : Triggered when the dragged element enters the target area
• dragover : Continuously triggered when dragging within the target area
• drop : fired when the element is released in the target area
• dragleave : Triggered when the dragged element leaves the target area

You only need to bind the corresponding processing functions on these key nodes to control the entire drag-and-drop behavior. For example, set dragged data in dragstart , and handle data reception and logical execution in drop .

Implement a simple drag-and-drop example

Suppose you want to drag one div into another div, the most basic approach is:

 <div id="draggable" draggable="true">Drag me to try</div>
<div id="droptarget">Put it here</div>

<script>
const draggable = document.getElementById(&#39;draggable&#39;);
const droptarget = document.getElementById(&#39;droptarget&#39;);

draggable.addEventListener(&#39;dragstart&#39;, function (e) {
  e.dataTransfer.setData(&#39;text/plain&#39;, &#39;This is the dragged data&#39;);
});

droptarget.addEventListener(&#39;dragover&#39;, function (e) {
  e.preventDefault(); // Default behavior must be blocked to trigger drop
});

droptarget.addEventListener(&#39;drop&#39;, function (e) {
  e.preventDefault();
  const data = e.dataTransfer.getData(&#39;text/plain&#39;);
  console.log(&#39;Received data:&#39;, data);
});
</script>

A few points to note:

• To make the element draggable, draggable="true" must be added
• In dragover , be sure to call e.preventDefault() , otherwise the drop will not take effect
• dataTransfer is an object used to pass data, supports multiple formats, and commonly used text

Frequently Asked Questions and Notes

When using this API, some details are easy to ignore but are important:

• ? The processing methods are different when dragging and dropping files
  If you are dragging files (such as images) from the operating system, you mainly rely on listening to drop events to get FileList object, rather than through setData/GetData .

• ? Don't confuse dragover and drop
  Many people think that dragover will only be triggered once, but in fact it is triggered continuously. If you do too much in it, it may affect performance.

• ? Some browser default behavior needs to be blocked manually
  For example, when dragging a link or image, the browser may open a new page or download it by itself. At this time, you need to call preventDefault in dragstart or drop to prevent these behaviors.

• ? Cross-drag and drop may be restricted
  If you drag content from other websites, some browsers have security policy restrictions, especially when it comes to sensitive data.

Basically that's it. The Drag and Drop API doesn't seem complicated, but it has to deal with many boundary situations in actual applications, especially compatibility and user experience. By mastering these core events and techniques, you can create practical drag-and-drop functions.

The above is the detailed content of What is the HTML5 Drag and Drop API?. For more information, please follow other related articles on the PHP Chinese website!