行拖动的实现思路非常简单，选中一行，往上拖就与上面的行交换位置，往下拖就与下面的行交换位置。问题是如何得到交换行。我见过一个非常详细的教程，它会把表格里的每一行的高度与Y坐标计算出来，换言之，都时是比较e.pageX是否在[rowTop,rowBottom]区间之内。但这也带来第二个问题，有多少行就有多个这样的区间。于是解法就变成取事件源对象，然后再往上取其父对象，如果其父对象是TR元素，就取其[rowTop,rowBottom]区间....思路非常直接，同时也客观做出一个限制——不能使用代理拖动。先不谈是拖动代理还是拖动实物，光是在移动鼠标的过程要做的计算量就非常大，幸好还在IE的承受范围之内。有更好的方法吗？
人之所以先入为主，因为他就握着这么几把锁匙。如果他手上的锁匙非常多时，他在开门时就会稍微停下来，认真挑选了。因此熟悉掌握越多的原生API就越好，我们就才获取更优的选项。换一个思路，在拖动时（mousedown）保存当前行及其样式与坐标，拖动中取得鼠标所在位置上的元素，这个元素是使用一个巧妙的API取得document.elementFromPoint(x,y)。通常情况，我们取得的是TD，当然如果你在里面塞进一个DIV，那就是DIV罗。然后我们再取得其TR元素，然后比较mousedown时保存的TR元素是不是同一个元素，不是同一个元素，我们才做进一步的操作。这时我们就要判其是向上移向下移，简单的减法而已。接着是交换两行，使用insertBefore。最后当mouseup时，还原行的样式就是！由于没有复杂的坐标计算，整个程式出奇的高效！
<!doctype html>
<html>
<head>
<title>表格行拖动</title>
<script>
window.onload = function(){
//绑定事件
var addEvent = document.addEventListener ? function(el,type,callback){
el.addEventListener( type, callback, !1 );
} : function(el,type,callback){
el.attachEvent( "on" + type, callback );
}
//移除事件
var removeEvent = document.removeEventListener ? function(el,type,callback){
el.removeEventListener( type, callback );
} : function(el,type,callback){
el.detachEvent( "on" + type, callback);
}
//精确获取样式
var getStyle = document.defaultView ? function(el,style){
return document.defaultView.getComputedStyle(el, null).getPropertyValue(style)
} : function(el,style){
style = style.replace(/\-(\w)/g, function($, $1){
return $1.toUpperCase();
});
return el.currentStyle[style];
}
var dragManager = {
clientY:0,
draging:function(e){//mousemove时拖动行
var dragObj = dragManager.dragObj;
if(dragObj){
e = e || event;
if(window.getSelection){//w3c
window.getSelection().removeAllRanges();
}else if(document.selection){
document.selection.empty();//IE
}
var y = e.clientY;
var down = y > dragManager.clientY;//是否向下移动
var tr = document.elementFromPoint(e.clientX,e.clientY);
if(tr && tr.nodeName == "TD"){
tr = tr.parentNode
dragManager.clientY = y;
if( dragObj !== tr){
tr.parentNode.insertBefore(dragObj, (down ? tr.nextSibling : tr));
}
};
}
},
dragStart:function(e){
e = e || event;
var target = e.target || e.srcElement;
if(target.nodeName === "TD"){
target = target.parentNode;
dragManager.dragObj = target;
if(!target.getAttribute("data-background")){
var background = getStyle(target,"background-color");
target.setAttribute("data-background",background)
}
//显示为可移动的状态
target.style.backgroundColor = "#ccc";
target.style.cursor = "move";
dragManager.clientY = e.clientY;
addEvent(document,"mousemove",dragManager.draging);
addEvent(document,"mouseup",dragManager.dragEnd);
}
},
dragEnd:function(e){
var dragObj = dragManager.dragObj
if (dragObj) {
e = e || event;
var target = e.target || e.srcElement;
if(target.nodeName === "TD"){
target = target.parentNode;
dragObj.style.backgroundColor = dragObj.getAttribute("data-background");
dragObj.style.cursor = "default";
dragManager.dragObj = null;
removeEvent(document,"mousemove",dragManager.draging);
removeEvent(document,"mouseup",dragManager.dragEnd);
}
}
},
main:function(el){
addEvent(el,"mousedown",dragManager.dragStart);
}
}
var el = document.getElementById("table");
dragManager.main(el);
}
</script>
<style>
.table{
width:60%;
border: 1px solid red;
border-collapse: collapse;
}
.table td{
border: 1px solid red;
height: 20px;
}
</style>
</head>
<body>
<h1>表格行拖动</h1>
<table id="table" class="table">
<tbody>
<tr>
<td>1</td>
<td>One</td>
<td>dom.require</td>
</tr>
<tr id="2" >
<td class="2">2</td>
<td>Two</td>
<td>ControlJS </td>
</tr>
<tr id="3" >
<td class="3">3</td>
<td>Three</td>
<td>HeadJS</td>
</tr>
<tr id="4" >
<td class="4">4</td>
<td>Four</td>
<td>LAB.js</td>
</tr>
<tr id="5" >
<td class="5">5</td>
<td>Five</td>
<td>$script.js</td>
</tr>
<tr id="6" >
<td class="6">6</td>
<td>Six</td>
<td>NBL.js</td>
</tr>
</tbody>
</table>
</body>
</html>
运行代码
window.onload = function(){
//绑定事件
var addEvent = document.addEventListener ? function(el,type,callback){
el.addEventListener( type, callback, !1 );
} : function(el,type,callback){
el.attachEvent( "on" + type, callback );
}
//移除事件
var removeEvent = document.removeEventListener ? function(el,type,callback){
el.removeEventListener( type, callback );
} : function(el,type,callback){
el.detachEvent( "on" + type, callback);
}
//精确获取样式
var getStyle = document.defaultView ? function(el,style){
return document.defaultView.getComputedStyle(el, null).getPropertyValue(style)
} : function(el,style){
style = style.replace(/\-(\w)/g, function($, $1){
return $1.toUpperCase();
});
return el.currentStyle[style];
}
var dragManager = {
clientY:0,
draging:function(e){//mousemove时拖动行
var dragObj = dragManager.dragObj;
if(dragObj){
e = e || event;//清除选区
if(window.getSelection){//w3c
window.getSelection().removeAllRanges();
}else if(document.selection){
document.selection.empty();//IE
}
var y = e.clientY;
var down = y > dragManager.clientY;//是否向下移动
var tr = document.elementFromPoint(e.clientX,e.clientY);
if(tr && tr.nodeName == "TD"){
tr = tr.parentNode
dragManager.clientY = y;
if( dragObj !== tr){
tr.parentNode.insertBefore(dragObj, (down ? tr.nextSibling : tr));
}
};
}
},
dragStart:function(e){
e = e || event;
var target = e.target || e.srcElement;
if(target.nodeName === "TD"){
target = target.parentNode;
dragManager.dragObj = target;
if(!target.getAttribute("data-background")){
var background = getStyle(target,"background-color");
target.setAttribute("data-background",background)
}
//显示为可移动的状态
target.style.backgroundColor = "#ccc";
target.style.cursor = "move";
dragManager.clientY = e.clientY;
addEvent(document,"mousemove",dragManager.draging);
addEvent(document,"mouseup",dragManager.dragEnd);
}
},
dragEnd:function(e){
var dragObj = dragManager.dragObj
if (dragObj) {
e = e || event;
var target = e.target || e.srcElement;
if(target.nodeName === "TD"){
target = target.parentNode;
dragObj.style.backgroundColor = dragObj.getAttribute("data-background");
dragObj.style.cursor = "default";
dragManager.dragObj = null;
removeEvent(document,"mousemove",dragManager.draging);
removeEvent(document,"mouseup",dragManager.dragEnd);
}
}
},
main:function(el){
addEvent(el,"mousedown",dragManager.dragStart);
}
}
var el = document.getElementById("table");
dragManager.main(el);
}