title: WKWebView - change viewport?
body: <p>I am currently running the following code to set the viewport of my WKWebView:</p>
  
  <pre><code>NSString* viewPortjs = [NSString stringWithFormat:@"document.querySelector('meta[name=viewport]').setAttribute('content', 'width=%dpx;', false);", (int) webView.frame.size.width];
  [webView evaluateJavaScript:viewPortjs completionHandler:nil];
  </code></pre>
  
  <p>I can see that if the code finds the selector <code>viewport</code>, it'll correctly set it, but I want to add the ability to add this line to the DOM if it is not present. I am a noob when it comes to Javascript, so I'm not sure how to change this code to handle the case if that selector is not present and add it. Can anyone help me out? Thanks!</p>