jQuery example to update a form on focus

application.js

/*Content originally from CodeSchool's "try jQuery" lesson. http://try.jquery.com/levels/4/challenges/16  */
$(document).ready(function() {
/*  
* this first part fetches the price and multiplies for the number input in the form
*/
  $("#nights").on("keyup", function() {
    var nights = +$(this).val();
    var dailyPrice = +$(this).closest(".tour").data("daily-price");
    $("#total").text(nights * dailyPrice);
    $("#nights-count").text($(this).val());
  });
/*  
* This is a reset, whenever the form is focused the value is reset to 7
*/
  $("#nights").on("focus", function() {
    $(this).val(7);
  });
});

index.html

<!-- Content originally from CodeSchool's "try jQuery" lesson. http://try.jquery.com/levels/4/challenges/16  -->
<div class="tour" data-daily-price="357">
  <h2>Paris, France Tour</h2>
  <p>$<span id="total">2,499</span> for <span id="nights-count">7</span> Nights</p>
  <p>
    <label for="nights">Number of Nights</label>
  </p>
  <p>
    <input type="number" id="nights" value="7">
  </p>
</div>