title: 'undefined' is not a function (evaluating '$(document).on')
body: <p>I am trying to use this script:</p>
  
  <pre><code>&lt;script&gt;
  var original_value = Number($('#ProductPrice').text().replace(/[^0-9.]+/g,""));
  
  $(document).on('keyup', '#ProductPrice', function() {
  if (Number($('#ProductPrice').text().replace(/[^0-9.]+/g,"")) &gt; original_value) {
      $("#ProductPrice").css("color","red");
  } else {
      $("#ProductPrice").css("color", "black");   
  }
  });
  &lt;/script&gt;
  </code></pre>
  
  <p>I keep getting an error:'undefined' is not a function (evaluating '$(document).on')</p>
  
  <p>Help?</p>