title: What value is not strictly equal to itself & NaN in javascript
body: <p>I need that value of a variable such that i get alert "Yes", in the code.</p>
  
  <pre><code>var a;
  
  // set the value of a here ...
  a=?
  
  // don't edit the code below:
  if (a === a) { 
      alert('No!'); 
  } else {
      if (isNaN(a)) {
          alert('Not again!');
      }
      else { 
          alert('Yes');
      }
  }
  </code></pre>
  
  <p>What is a?</p>