title: RegExp.Test always returning false
body: <p>I have the following code at JSfiddle:</p>
  
  <p><a href="http://jsfiddle.net/ACG2D/" rel="noreferrer">http://jsfiddle.net/ACG2D/</a></p>
  
  <pre><code>$(document).ready(function() {
      $('.testThis').click(function() {
          $('.regexValidation').each(function() {
              if ($(this).val() != "" || $(this).val() != null) {
                  // Check the regex
                  var expression = new RegExp('/^[0-9a-z_]+$/i');
                  var myVal = $(this).val();
                  if (expression.test(myVal) == true) {
                      // All is okay
                      alert("OK");
                  } else {
                      alert("Error");
                  }
              }
          });
      });    
  });
  </code></pre>
  
  <p>The intended plan is to only let alphanumeric and underscores through. Disallowing spaces and punctuation etc.</p>
  
  <p>I can't figure out why this is going wrong, but it always returns false for the test.</p>