read only</span><a href="#scope"><span class="identifier">scope</span></a>:<a class="type" title="String - The basic String class." href="../../String.html">String</a></code></h3><div class="doc"><p>Returns a unique identifier for a service worker registration. This must be on the same origin as the document that registers the <code><a href="../../js/html/ServiceWorker.html#ServiceWorker">ServiceWorker</a></code>.</p></div></div><div class="field "><a name="updateViaCache"></a><h3 class="anchor"><code><span