在web开发中，我们要实现拖放效果，需要借助javascript。今天让我们使用html5实现它：
先看html核心代码:
复制代码代码如下:
<div>
<p>把黄色小方块拖入到红色大方框中</p>
</div>
<div id="item" draggable="true">
</div>
<div id="drop">
</div>
draggable属性是html5新增加的，它有三个值true,false,auto. true是可以拖，false是不可以，auto由用户浏览器是否支持而定。更多请可以参考官方文档.
加上一点儿样式:
复制代码代码如下:
<style type="text/css">
#drop
{
width: 300px;
height: 200px;
background-color: #ff0000;
padding: 5px;
border: 2px solid #000000;
}
#item
{
width: 100px;
height: 100px;
background-color: #ffff00;
padding: 5px;
margin: 20px;
border: 1px dashed #000000;
}
*[draggable=true] {
-moz-user-select:none;
-khtml-user-drag: element;
cursor: move;
}
*:-khtml-drag {
background-color: rgba(238,238,238, 0.5);
}
</style>
然后我们来看javascript:
复制代码代码如下:
function listenevent(eventtarget, eventtype, eventhandler) {
if (eventtarget.addeventlistener) {
eventtarget.addeventlistener(eventtype, eventhandler,false);
} else if (eventtarget.attachevent) {
eventtype = "on" + eventtype;
eventtarget.attachevent(eventtype, eventhandler);
} else {
eventtarget["on" + eventtype] = eventhandler;
}
}
// cancel event
function cancelevent (event) {
if (event.preventdefault) {
event.preventdefault();
} else {
event.returnvalue = false;
}
}
// cancel propagation
function cancelpropagation (event) {
if (event.stoppropagation) {
event.stoppropagation();
} else {
event.cancelbubble = true;
}
}
window.onload=function() {
var target = document.getelementbyid("drop");
listenevent(target,"dragenter",cancelevent);
listenevent(target,"dragover", dragover);
listenevent(target,"drop",function (evt) {
cancelpropagation(evt);
evt = evt || window.event;
evt.datatransfer.dropeffect = 'copy';
var id = evt.datatransfer.getdata("text");
target.appendchild(document.getelementbyid(id));
});
var item = document.getelementbyid("item");
item.setattribute("draggable", "true");
listenevent(item,"dragstart", function(evt) {
evt = evt || window.event;
evt.datatransfer.effectallowed = 'copy';
evt.datatransfer.setdata("text",item.id);
});
};
function dragover(evt) {
if (evt.preventdefault) evt.preventdefault();
evt = evt || window.event;
evt.datatransfer.dropeffect = 'copy';
return false;
}
由上面的代码我们看使用一组html5 提供的拖放events,直接来看下面:
dragstart
drag event starts.
drag
during the drag operation.
dragenter
drag is over the target; used to determine if target will accept drop.
dragover
drag is over target; used to determine feedback to user.
drop
drop occurs.
dragleave
drag leaves target.
dragend
drag operation ends.
定义了相关的事件，来实现想要功能。上面的js不难看懂。
你可以自己试一下，目前在opera支持最好，ie效果并不好。
希望对您web开发有帮助.
