title: What happens if I put unavailable value in javascript variable?
body: <pre><code>function() {
    var id1 = document.getElementById("usrEmailId").value
    var id2 = document.getElementById("usrEmailIdSecondary").value
    var id3 = document.getElementById("emailId").value
  }
  </code></pre>
  
  <p>Here, on a HTML page, I have Email Id capture field. There are two pages and one page has only the element <code>usrEmailId</code> and <code>usrEmailIdSecondary</code> and the other page has the elements <code>usrEmailId</code> and <code>emailI</code>. So what will happen to variable <code>id3</code> in case of first page. What will be stored in it? (NULL, undefined, or  empty)?</p>