使div总居中
<!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" >
<head>
??? <title>無標題頁</title>
</head>
<body>
<div style="width:2000px;height:2000px;"></div>
<div id="div" style="position:absolute; background-color:Green; width:100px; height:100px;"></div>
</body>
</html>
<script type="text/javascript">
??? function $(id) { return document.getElementById(id); };
??? var div = $("div");
??? function reset() {
??????? var d = document.documentElement;
??????? //? 首先取得頁面現在的左上角相對位置
??????? var x1 = d.scrollLeft;
??????? var y1 = d.scrollTop;
??????? var w1 = d.clientWidth;
??????? var h1 = d.clientHeight;
??????? //? 取得浮動層的信息
??????? var w = parseInt(div.style.width);
??????? var h = parseInt(div.style.height);
??????? var x = Math.ceil((w1 - w) / 2) + x1;
??????? var y = Math.ceil((h1 - h) / 2) + y1;
??????? //? 設置位置
??????? div.style.left = x;
??????? div.style.top = y;
??? }
??? window.onresize = reset;
??? window.onscroll = reset;
??? reset();
</script>
?
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