title: Uncaught TypeError: Cannot read property 'data' of null using array
body: <p>My JS is throwing this error even when i'm checking if it's null or not. Maybe one of you guys could help me with this one.</p>
  
  <pre><code>if (typeof(this.callbacks['changed']) !== 'undefined') {
          if (typeof(obj['item']['data']) !== 'undefined' &amp;&amp; 
             (typeof(obj['item']['data'] != null))) {
              this.callbacks['changed'](row, obj['item']['data']);
          }
      }
  </code></pre>
  
  <p>This error: </p>
  
  <blockquote>
    <p>Uncaught TypeError: Cannot read property 'data' of null </p>
  </blockquote>
  
  <p>already starts here: <code>&amp;&amp; (typeof(obj['item']['data'] != null)</code></p>