Condition checking on like button of face book on page load

i made a fan gate using code below.it is working fine for website.when i used this code on facebook tab.it is not redirecting facebook page in javascript.my javascript code is given below:-




<script type="text/javascript">

$(document).ready(function() {
FB.login(function(response) {
if (response.status == 'connected') {
var user_id = response.authResponse.userID;
var page_id = "XXXXXXXX"; // coca cola page https://www.facebook.com/cocacola
var fql_query = "SELECT uid FROM page_fan WHERE page_id=" + page_id + " and uid=" + user_id;

FB.api('/me/likes/' + page_id, function(response) {
if (response.data[0]) {
//top.window.open("FirstPage.aspx", "_self");
//$("#container_like").show();
// document.getElementById("<% =btnUnlike.ClientID %>").click();
window.location.href("FirstPage.aspx");
} else {
//$("#container_notlike").show();
// document.getElementById("<% =btnLike.ClientID %>").click();
//top.window.open("Like.aspx", "_self")
window.location.href("Like.aspx");
}
});
} else {
// user is not logged in
}
});
});
</script>