top
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Window top 属性
定义和用法
Top属性返回当前窗口的最顶层浏览器窗口。
语法
window.top
浏览器支持
所有主要浏览器都支持 top 属性
实例
当点击"Check window"按钮，check()被调用，并检查当前窗口的状态：
<html>
<head>
<script>
function check()
{
if (window.top!=window.self)
{
document.write("<p>This window is not the topmost window! Am I in a frame?</p>")
}
else
{
document.write("<p>This window is the topmost window!</p>")
}
}
</script>
</head>
<body>
<input type="button" onclick="check()" value="Check window">
</body>
</html>
<head>
<script>
function check()
{
if (window.top!=window.self)
{
document.write("<p>This window is not the topmost window! Am I in a frame?</p>")
}
else
{
document.write("<p>This window is the topmost window!</p>")
}
}
</script>
</head>
<body>
<input type="button" onclick="check()" value="Check window">
</body>
</html>