Document.referrer for base domain
<p>I know I can grab the entire referring url by using:</p>

<pre><code>document.referrer
</code></pre>

<p>But how would I only grab the base domain of the referrer??  So:</p>

<pre><code>if(document.referrer === subdomain.domain.com){

}
</code></pre>

<p>So all referring urls coming from that main domain would work and all strings coming after the base domain are ignored.</p>
