ondragstart event


ondragstart Event

Instance

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<style>
.droptarget {
    float: left; 
    width: 100px; 
    height: 35px;
    margin: 15px;
    padding: 10px;
    border: 1px solid #aaaaaa;
}
</style>
</head>
<body>

<p>在两个矩形框中来回拖动 p 元素:</p>
<div class="droptarget" ondrop="drop(event)" ondragover="allowDrop(event)">
  <p ondragstart="dragStart(event)" ondragend="dragEnd(event)" draggable="true" id="dragtarget">拖动我!</p>
</div>
<div class="droptarget" ondrop="drop(event)" ondragover="allowDrop(event)"></div>
<p style="clear:both;"><strong>注意：</strong>Internet Explorer 8 及更早 IE 版本或 Safari 5.1 及更早版本的浏览器不支持 drag 事件。</p>
<p id="demo"></p>
<script>
function dragStart(event) {
    event.dataTransfer.setData("Text", event.target.id);
    document.getElementById("demo").innerHTML = "开始拖动 p 元素";
}
function dragEnd(event) {
    document.getElementById("demo").innerHTML = "完成 p 元素的拖动。";
}
function allowDrop(event) {
    event.preventDefault();
}
function drop(event) {
    event.preventDefault();
    var data = event.dataTransfer.getData("Text");
    event.target.appendChild(document.getElementById(data));
}
</script>

</body>
</html>

Run Instance»

Click "Run Instance" button to view an online instance

More examples are included at the bottom of this article.

Definition and Usage

ondragstart event is triggered when the user starts dragging an element or selected text.

Drag and drop is a very common feature in HTML5. More information can be found in our HTML HTML5 drag and drop in tutorial.

Note: In order to make an element draggable, you need to use the HTML5draggable 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 - Fires when 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 container range of another object
    • ondragleave - This event is triggered when the object being dragged by the mouse leaves the range of its container
    • ondrop - This event is triggered when the mouse button is released during a drag process

Browser support

Note: When dragging an element, the ondragover event will be triggered every 350 milliseconds.

12.png

Syntax

HTML:

<element ondragstart="myScript ">Try it

In JavaScript:

object.ondragstart=function(){myScript };Try it

In JavaScript, use the addEventListener() method:

object.addEventListener("dragstart", myScript);Try it

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


More instances

Instance

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<style>
.droptarget {
    float: left; 
    width: 100px; 
    height: 35px;
    margin: 15px;
    padding: 10px;
    border: 1px solid #aaaaaa;
}
</style>
</head>
<body>

<p>在两个矩形框中来回拖动 p 元素:</p>
<div class="droptarget">
	<p draggable="true" id="dragtarget">拖动我!</p>
</div>
<div class="droptarget"></div>
<p style="clear:both;"><strong>注意：</strong>Internet Explorer 8 及更早 IE 版本或 Safari 5.1 及更早版本的浏览器不支持 drag 事件。</p>
<p id="demo"></p>
<script>
/* 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));
    }
});
</script>

</body>
</html>

Running instance»

Click the "Run Example" button to view the online example


Related Pages

HTML Tutorial: HTML5 Drag and Drop

HTML Reference Manual: HTML draggable attribute