Detecting request without using document.domain

Detecting request without using document.domain

I have a script placed in a website.
<script>
var domain = document.domain;
/* script related to website...*/
</script>
This returns the website domain to my site using some script. Now, how can
we detect the domain name without using document.domain. I cannot use
document.domain as part of variable as it can easily be changed by anyone
and script is no more secure. How can I check whether my script is placed
in designated website.I am having list of website names in database? I am
using cakephp framework.