Ondragstart event in HTML5 that is triggered when the user starts dragging an element or selected text

Example

Executed when the user starts dragging the

elementJavaScript :

<p draggable="true" ondragstart="myFunction(event)">拖动我!</p>

Definition and usage

ondragstart Event Fired when the user starts dragging an element or selected text.

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 - Fires when the user starts dragging the element

• ondrag - Fires when the element is being dragged

• ##ondragend - The user completes dragging the element Triggered after moving

Events triggered when the target is released:

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

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

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

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

Syntax

HTML:

<element ondragstart="myScript">

JavaScript:

object.ondragstart=function(){myScript};

In JavaScript, use the addEventListener() method:

object.addEventListener("dragstart", myScript);

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

Technical details

Whether bubbling is supported:YesCan be canceled :YesEvent type:DragEventSupported 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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