screen對象
screen對象包含客戶端瀏覽器屏幕的相關信息
screen對象常見屬性如下：availHeight:返回屏幕的高度(除window系統任務欄之外)
availWidth：返回屏幕的寬度(除window系統任務欄之外)
height:返回屏幕的高度
width:返回屏幕的寬度
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>screen對象</title>
</head>
<body>
<script type="text/javascript">
window.document.write("屏幕高度"+window.screen.availHeight);
window.document.write("屏幕寬度"+window.screen.availWidth);
window.document.write("屏幕高度"+window.screen.height);
window.document.write("屏幕寬度"+window.screen.width);
</script>
</body>
</html>