title: Uncaught TypeError: Cannot read property 'toLowerCase' of undefined
body: <pre><code>$('#sum').keydown(function(){
             updateResultPrice(); 
          });
  
          function updateResultPrice() {
              ajax('/payment/summ', 'price='+$(this).val());
          }
  </code></pre>
  
  <p>Not working! Console log print:
  Uncaught TypeError: Cannot read property 'toLowerCase' of undefined </p>