title: Google Analytics (gtag) cross-domain
body: <p>I've an website with two domains, everything is redirected using JQuery (no a href="xxx"), how can i pass the _ga parameter on URL manually? I just want to get the client ID and pass with jquery like:</p>
  
  <pre><code>  window.location
    .replace('https://mynewdomain.com/?_ga=' + CLIENTID);
    return;
  </code></pre>
  
  <p>on mynewdomain.com i have:</p>
  
  <pre><code>      gtag('config', 'UA-XXXXXX-X', {'linker': {'domains': ['olddomain.com','mynewdomain.com'], 'accept_incoming': true}});
  </code></pre>
  
  <p>I'm really going crazy with this...</p>