拖动是一件非常酷的事情。你点击某个对象，并按住鼠标不放，将鼠标移动到另一个区域，然后释放鼠标按钮将对象放在这里。
下面是一个简单的案例：
HTML部分：注意，拖动元素一定要为绝对定义，即position = absolute;
JS部分（dome.js）：
var EventUtil = {
// 获取事件和目标
getEvent : function (event) {
return event ? event : window.event;
},
getTarget : function (event) {
return event.target || event.srcElement;
},
// 添加监听事件
addEvent : function (element, type, handler) {
if (element.addEventListener)
{
element.addEventListener(type, handler, false);
} else if (element.attachEvent)
{
element.attachEvent("on" + type, handler);
}
},
// 注销监听事件
delEvent : function (element, type, handler) {
if (element.removeEventListener)
{
element.removeEventListener(type, handler, false);
} else if (element.detachEvent)
{
element.detachEvent("on" + type, handler);
}
}
}
var DragDrop = function () {
// 判断DOM元素是否正在被拖动的标志
var dragging = null;
// DOM元素左上角与鼠标指针的差值
diffX = 0;
diffY = 0;
function handleEvent(event) {
event = EventUtil.getEvent(event);
var target = EventUtil.getTarget(event);
switch (event.type) {
case "mousedown" :
// 判断DOM元素的class中是否含有draggable属性
if (target.className.indexOf("draggable") > -1) {
dragging = target;
diffX = event.clientX - target.offsetLeft;
diffY = event.clientY - target.offsetTop;
}
break;
case "mousemove" :
if (dragging != null) {
target.style.left = event.clientX - diffX + "px";
target.style.top = event.clientY - diffY + "px";
}
break;
case "mouseup" :
dragging = null;
break;
}
}
return {
enable : function () {
EventUtil.addEvent(document, "mousedown", handleEvent);
EventUtil.addEvent(document, "mousemove", handleEvent);
EventUtil.addEvent(document, "mouseup", handleEvent);
},
disable : function () {
EventUtil.delEvent(document, "mousedown", handleEvent);
EventUtil.delEvent(document, "mousemove", handleEvent);
EventUtil.delEvent(document, "mouseup", handleEvent);
}
}
}();
DragDrop.enable();
这里需要讲解的是diffX和diffY，它们表示元素左上角与鼠标指针的差值。
diffX = 鼠标的x坐标 - 元素对象的offsetLeft
diffY = 鼠标的y坐标 - 元素对象的offsetTop
以上就是本文的全部内容，希望对大家的学习有所帮助。
