title: If-statement condition checking on != "undefined" fails
body: <p>I'm trying to generate some HTML content for a google maps infowindow. I have 7 values which is supposed to be displayed if they do not equal null, undefined or "" (empty string).</p>
  
  <p>But apparently my <code>if(e.Property != null || e.Property != "undefined" || e.Property == "")</code> doesn't work when a <code>Property</code> is <code>undefined</code>. Mostly the case is that <code>e.Email</code> is undefined. So instead of skipping that part, my code still inserts the <code>html + "&lt;br /&gt;</code> part. And when I <code>alert()</code> the e.Email it returns <code>undefined</code> which it's supposed to catch and skip if that was the case.</p>
  
  <p>I have tried writting <code>if(typeof e.Property != null || typeof e.Property != "undefined" || typeof e.Property == "")</code>, but that made no difference.</p>
  
  <pre><code>// 'e ' is JSON object
  var generateHTML = {
      init: function(e) {
          if (e != null || e != "undefined"){
              generateHTML.check(e);
          }
      },
      check: function (e) {
          if(e.Title != null || e.Title != "undefined" || e.Title == ""){
              html = html + "&lt;b&gt;"+e.Title+"&lt;/b&gt;";
          }
          if(e.Address != null || e.Address != "undefined" || e.Address == ""){
              html = html +"&lt;br /&gt;"+ e.Address;
          }
          if(e.Zipcode != null || e.Zipcode != "undefined" || e.Zipcode == ""){
              html = html +"&lt;br /&gt;"+ e.Zipcode+", ";
          }
          if(e.City != null || e.City != "undefined" || e.City == ""){
              html = html + e.City;
          }
          if(e.Phone != null || e.Phone != "undefined" || e.Phone == ""){
              html = html +"&lt;br /&gt;"+ e.Phone;
          }
          if(e.Email != null || e.Email != "undefined" || e.Email == ""){
              html = html +"&lt;br /&gt;"+ e.Email;
          }
          if(e.WebAddress != null || e.WebAddress != "undefined" || e.WebAddress == ""){
              html = html +"&lt;br /&gt;"+ e.WebAddress;
          }
          return html;
      }
  };
  </code></pre>