title: iOS WebKit - DataCloneError: The object can not be cloned
body: <p>When working with WKWebView of iOS WebKit, I encountered an error when I tried to <code>postMessage</code> back to my <code>WKScriptMessageHandler</code> in a code like</p>
  
  <pre><code>window.webkit.messageHandlers.thisHandler.postMessage(message);
  </code></pre>
  
  <p>where message is a Javascript object (or in iOS developer's eyes, a dictionary) and the error is:</p>
  
  <pre><code>WKJavaScriptExceptionMessage=DataCloneError: The object can not be cloned.
  </code></pre>
  
  <p>It was quite confusing what this is about and I couldn't google out any useful information. </p>