[Introduction] Drag and drop events Through drag and drop events, we can control drag and drop many things. Which element or where the drag event occurs is the most critical. Some events are fired on the dragged element, and some events are fired on the drop target. When dragging an element, the events triggered are:
Drag events
Through drag events, we can control dragging many things. Which element or where the drag event occurs is the most critical. Some events are fired on the dragged element, and some events are fired on the drop target. When an element is dragged, the events triggered are: dragstart event, drag event and dragend event.
When you press the mouse button and start moving the mouse, the dragstart event will be triggered on the dragged element. At this time, the cursor changes to a "cannot place" symbol (there is a backslash in the circle), indicating that the element cannot be placed on its own door. When dragging starts, JavaScript code can be run through the ondragstart event handler.
After the dragstart event is triggered, the drag event will be triggered immediately, and the drag event will continue to be triggered while the element is being dragged. This event is similar to the mousemove and touchmove events. When dragging stops (whether the element is placed on a valid drop target or an invalid drop target), the dragend event occurs.
The targets of the three events mentioned above are all triggered by the dragged element. By default, the browser does not change the appearance of the dragged element during dragging. But you can modify it yourself. However, most browsers create a semi-transparent copy of the element being dragged, which always follows the cursor. When an element is dragged to a valid drop target, the events that will be triggered are: dragenter event, dragover event and dragleave or drop event.
As long as an element is dragged to the drop target, the dragenter event will be triggered (similar to the mouseover event). This is followed by the dragover event, and when the dragged element is still moving within the range of the drop target, the dragover event will be triggered continuously. If the element is dragged out of the drop target, the dragover event no longer occurs, but the dragleave event is triggered (similar to the mouseout event). If the element is placed in the drop target, the drop event will be triggered instead of the dragleave event. The targets of dragenter events, dragover events, and dragleave or drop events are all elements that serve as drop targets.
Custom placement target
When dragging an element past some invalid placement targets, you can see a special mouse gesture ( A backslash in the circle) indicates that it cannot be placed. Although all elements support drop target events, these elements are not allowed to be dropped by default. If an element is dragged past an element that is not allowed to be dropped, no matter what the user does, the drop event will not occur. However, you can make any element a valid drop target by overriding the default behavior of the dragenter and dragover events.
After overriding the default behavior, you will find that when dragging the element to the drop target, the cursor changes to a symbol that allows placement. In Firefox 3.5+, the default behavior of a drop event is to open the url that was dropped on the drop target. If you drag an image onto the drop target, the page will redirect to the image file. If you drag and drop text onto the drop target, an invalid url error will result. Therefore, in order for Firefox to support normal drag and drop, it is necessary to cancel the default behavior of the drop event and prevent the URL of the dragged element from being opened. A small example is as follows
HTML code
The above is the detailed content of HTML5 explanation of drag events dragstart, drag and dragend. For more information, please follow other related articles on the PHP Chinese website!

html5的div元素默认一行不可以放两个。div是一个块级元素,一个元素会独占一行,两个div默认无法在同一行显示;但可以通过给div元素添加“display:inline;”样式,将其转为行内元素,就可以实现多个div在同一行显示了。

html5中列表和表格的区别:1、表格主要是用于显示数据的,而列表主要是用于给数据进行布局;2、表格是使用table标签配合tr、td、th等标签进行定义的,列表是利用li标签配合ol、ul等标签进行定义的。

固定方法:1、使用header标签定义文档头部内容,并添加“position:fixed;top:0;”样式让其固定不动;2、使用footer标签定义尾部内容,并添加“position: fixed;bottom: 0;”样式让其固定不动。

html5中不支持的标签有:1、acronym,用于定义首字母缩写,可用abbr替代;2、basefont,可利用css样式替代;3、applet,可用object替代;4、dir,定义目录列表,可用ul替代;5、big,定义大号文本等等。

HTML5中画布标签是“<canvas>”。canvas标签用于图形的绘制,它只是一个矩形的图形容器,绘制图形必须通过脚本(通常是JavaScript)来完成;开发者可利用多种js方法来在canvas中绘制路径、盒、圆、字符以及添加图像等。

html5废弃了dir列表标签。dir标签被用来定义目录列表,一般和li标签配合使用,在dir标签对中通过li标签来设置列表项,语法“<dir><li>列表项值</li>...</dir>”。HTML5已经不支持dir,可使用ul标签取代。

3种取消方法:1、给td元素添加“border:none”无边框样式即可,语法“td{border:none}”。2、给td元素添加“border:0”样式,语法“td{border:0;}”,将td边框的宽度设置为0即可。3、给td元素添加“border:transparent”样式,语法“td{border:transparent;}”,将td边框的颜色设置为透明即可。

因为html5不基于SGML(标准通用置标语言),不需要对DTD进行引用,但是需要doctype来规范浏览器的行为,也即按照正常的方式来运行,因此html5只需要写doctype即可。“!DOCTYPE”是一种标准通用标记语言的文档类型声明,用于告诉浏览器编写页面所用的标记的版本。


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