The event ondragenter is triggered in H5 when the dragged element or selected text enters a valid drop target.

Example

Executed when the dragged element enters the drop targetJavaScript :

<div ondragenter="myFunction(event)"></div>

Definition and usage

ondragenter Event Triggered when the dragged element or selected text enters a valid drop target.

Ondragenter and ondragleave events can help users better understand the process of draggable elements entering and leaving the placement area. You can set different background colors when a draggable element enters and leaves the drop zone.

Drag and drop is a very common feature in HTML5. For more information, check out HTML5 Drag and Drop in our HTML tutorial.

Note: To make an element draggable, you need to use the HTML5 draggable attribute.

Tip: Links and images are draggable by default and do not require the draggable attribute.

The following events will be triggered during the drag and drop process:

Trigger events on the drag target (source element):

• ondragstart - User Fires when you start dragging the element

• ondrag - Fires when the element is being dragged

• ondragend - Fires after the user completes dragging the element

Events triggered when the target is released:

• ondragenter - This event is triggered when the object dragged by the mouse enters its container scope

• ondragover - This event is triggered when a dragged object is dragged within the scope of another object container

• ondragleave - When an object is dragged by the mouse This event is triggered when the object leaves the scope of its container

• ondrop - This event is triggered when the mouse button is released during a drag process

Browser support

The number in the table indicates the version number of the first browser that supports this event.

Syntax

HTML:

<element ondragenter="myScript">

JavaScript:

object.ondragenter=function(){myScript};

JavaScript, use the addEventListener() method :

object.addEventListener("dragenter", myScript);

Note: Internet Explorer 8 and earlier IE versions do not support the addEventListener() method.

Technical details

Whether bubbling is supported:	Yes
Can be canceled :	Yes
Event type:	DragEvent
Supported HTML tags:	All HTML elements

更多实例

实例

以下实例演示了所有的拖放事件：

/* 拖动时触发*/
document.addEventListener("dragstart", function(event) {
    //dataTransfer.setData()方法设置数据类型和拖动的数据
    event.dataTransfer.setData("Text", event.target.id);
    // 拖动 p 元素时输出一些文本
    document.getElementById("demo").innerHTML = "开始拖动 p 元素."; 
    //修改拖动元素的透明度
    event.target.style.opacity = "0.4";
});
//在拖动p元素的同时,改变输出文本的颜色
document.addEventListener("drag", function(event) {
    document.getElementById("demo").style.color = "red";
});
// 当拖完p元素输出一些文本元素和重置透明度
document.addEventListener("dragend", function(event) {
    document.getElementById("demo").innerHTML = "完成 p 元素的拖动";
    event.target.style.opacity = "1";
});
/* 拖动完成后触发 */
// 当p元素完成拖动进入droptarget,改变div的边框样式
document.addEventListener("dragenter", function(event) {
    if ( event.target.className == "droptarget" ) {
        event.target.style.border = "3px dotted red";
    }
});
// 默认情况下,数据/元素不能在其他元素中被拖放。对于drop我们必须防止元素的默认处理
document.addEventListener("dragover", function(event) {
    event.preventDefault();
});
// 当可拖放的p元素离开droptarget，重置div的边框样式
document.addEventListener("dragleave", function(event) {
    if ( event.target.className == "droptarget" ) {
        event.target.style.border = "";
    }
});
/*对于drop,防止浏览器的默认处理数据(在drop中链接是默认打开)
复位输出文本的颜色和DIV的边框颜色
利用dataTransfer.getData()方法获得拖放数据
拖拖的数据元素id("drag1")
拖拽元素附加到drop元素*/
document.addEventListener("drop", function(event) {
    event.preventDefault();
    if ( event.target.className == "droptarget" ) {
        document.getElementById("demo").style.color = "";
        event.target.style.border = "";
        var data = event.dataTransfer.getData("Text");
        event.target.appendChild(document.getElementById(data));
    }
});

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