How to display full screen of js control page and exit full screen display

<!DOCTYPE html>
<html>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<body>
<div style="margin:0 auto;height:600px;width:700px;">
<button > Full screen display and exit full screen display of js control page</button>
<div style="margin:0 auto;height:500px;width:700px; background:#ccc;" >
<h1>JS control page full screen display and exit full screen display</h1>
</div>
</div>
</body>
<script language="JavaScript">
("btn").onclick=function(){
    var elem = ("content");
    requestFullScreen(elem);
};
function requestFullScreen(element) {
    var requestMethod = || || || ;
    if (requestMethod) {
        (element);
    } else if (typeof !== "undefined") {
        var wscript = new ActiveXObject("");
        if (wscript !== null) {
            ("{F11}");
        }
    }
}
</script>
</html>