【发布时间】：2009-05-13 12:34:54
【问题描述】：
不要让下面的代码吓跑你。问题其实很简单，只有两行在闹：
为什么我的代码会生成 NaN 错误代码？我正在尝试从另一个变量值中减去一个变量值，因此元素的位置将是正确的。
变量从 jQuery position() 中获取它们的值，无论如何它应该是整数。
检查这些行：
// For some reason NaN error code gets generated when line below gets executed.
var posTop = Startpos.top - Stoppos.top;
var posLeft = Startpos.left - Stoppos.left;
完整代码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<meta http-equiv="Content-type" content="text/html; charset=iso-8859-1" />
<title>Drag drop 1</title>
<script type="text/javascript" src="js/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="js/jquery-ui-1.7.1.custom.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
var Startpos = new Array;
var Stoppos = new Array;
// Make images draggable.
$(".item").draggable({
// Elements cannot go outside #container
containment: 'parent',
// Make sure the element can only be dropped in a grid.
grid: [150,150],
// Find original position of dragged image.
start: function(event, ui) {
// Make sure picture always are on top when dragged (z-index).
$(this).css({'z-index' : '100'});
// Show start dragged position of image.
Startpos = $(this).position();
$("div#start").text("START: \nLeft: "+ Startpos.left + "\nTop: " + Startpos.top);
},
// Find position where image is dropped.
stop: function(event, ui) {
// Revert to default layer position when dropped (z-index).
$(this).css({'z-index' : '10'});
// Show dropped position.
Stoppos = $(this).position();
$("div#stop").text("STOP: \nLeft: "+ Stoppos.left + "\nTop: " + Stoppos.top);
}
});
$(".item").droppable({
drop: function(event, ui) {
// Dragged image gets swapped with dropped on image.
var prev_position = "#" + $(this).attr('id');
// For some reason NaN error code gets generated when line below gets executed.
var posTop = Startpos.top - Stoppos.top;
var posLeft = Startpos.left - Stoppos.left;
// Below variables will work. But unfortunately they
// doesn't give the correct numbers for the purpose.
// var posTop = Startpos.top;
// var posLeft = Startpos.left;
$(prev_position).css({'top' : posTop, 'left' : posLeft});
$("div#test").text("Passed variables. Top: " + posTop + " left: " + posLeft);
}
});
});
</script>
<style>
body {
}
#container {
position:relative;
width:480px;
border:1px solid #000;
}
.item {
position:relative;
width:150px;
height:150px;
z-index:10;
}
</style>
</head>
<body>
<div id="container">
<img id="productid_1" src="images/pic1.jpg" class="item" alt="" title="" /><img id="productid_2" src="images/pic2.jpg" class="item" alt="" title="" /><img id="productid_3" src="images/pic3.jpg" class="item" alt="" title="" /><img id="productid_4" src="images/pic4.jpg" class="item" alt="" title="" /><img id="productid_5" src="images/pic5.jpg" class="item" alt="" title="" /><img id="productid_6" src="images/pic6.jpg" class="item" alt="" title="" /><img id="productid_7" src="images/pic7.jpg" class="item" alt="" title="" /><img id="productid_8" src="images/pic8.jpg" class="item" alt="" title="" /><img id="productid_9" src="images/pic9.jpg" class="item" alt="" title="" />
</div>
<div style="clear:both;"></div>
<div id="start">Waiting...</div>
<div id="stop">Waiting...</div>
<div id="hover">Waiting...</div>
<div id="stop2">Waiting...</div>
<div id="test">Waiting...</div>
</body>
</html>
【问题讨论】：