The ondragover event in HTML5 is triggered when a draggable element or selected text is being dragged to the drop target.

Example

Triggered when the element is being dragged to the drop target:

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

Definition and usage

ondragover EventsOn draggable elements Or triggered when selected text is being dragged to the drop target.

By default, data/elements cannot be placed into other elements. If we want to implement the change function, we need to avoid the default processing method of the element. We can implement the ondragover event by calling the event.preventDefault() method.

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

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

Browser support

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

Syntax

HTML Medium:

<element ondragover="myScript">

JavaScript Medium:

object.ondragover=function(){myScript};

JavaScript Medium , use the addEventListener() method:

object.addEventListener("dragover", 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));
    }
});

The above is the detailed content of The ondragover event in HTML5 is triggered when a draggable element or selected text is being dragged to the drop target.. For more information, please follow other related articles on the PHP Chinese website!