title: Checking if undefined and null in jQuery
body: <p>I'm a bit confused when checking if null or undefined and if I should be using <code>!==</code> or <code>!=</code> and "undefined" or undefined.</p>
  
  <p>Here is some code I'm working on. Where am I going wrong with my null/unudefined etc?   </p>
  
  <pre><code>var c = (jQuery(this).prop("target") != null &amp;&amp; jQuery(this).prop("target") != undefined &amp;&amp; jQuery(this).prop("target").toLowerCase() == "_blank") ? 1 : 0;
  </code></pre>
  
  <p>Thanks</p>