Window top property
Window object Definition and Usage
Top property returns the current window topmost browser window.
grammar
window.top
Browser Support
All major browsers support top property
Examples
Examples
When click "Check window" button, check () is called, and check the current state of the window:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>本教程(w3big.com)</title>
<script>
function check(){
if (window.top!=window.self) {
document.write("<p>这个窗口不是最顶层窗口!我在一个框架?</p>")
}
else{
document.write("<p>这个窗口是最顶层窗口!</p>")
}
}
</script>
</head>
<body>
<input type="button" onclick="check()" value="检查窗口">
</body>
</html>
<html>
<head>
<meta charset="utf-8">
<title>本教程(w3big.com)</title>
<script>
function check(){
if (window.top!=window.self) {
document.write("<p>这个窗口不是最顶层窗口!我在一个框架?</p>")
}
else{
document.write("<p>这个窗口是最顶层窗口!</p>")
}
}
</script>
</head>
<body>
<input type="button" onclick="check()" value="检查窗口">
</body>
</html>
try it"
Window object