title: New Firebase failed: First argument must be a valid firebase URL and the path can't contain ".", "#", "$", "[", or "]"
body: <p>I am using Firebase to check presence, but the console throws up the following error:</p>
  
  <pre><code>New Firebase failed: First argument must be a valid firebase URL and the path can't contain ".", "#", "$", "[", or "]".
  </code></pre>
  
  <p>the following is the code:</p>
  
  <pre><code>new Firebase("https://123654789.firebaseio.com/123654/.info/connected").on('value', function(connectedSnap) {
    console.log(connectedSnap.val());
    if (connectedSnap.val() === true) {
      alert('I am connected!');
    } else {
      /* we're disconnected! */
      alert('not connected!');
    }
  });
  </code></pre>