未捕获的类型错误：无法读取 null 的属性“on”[重复]

我收到这个未捕获的类型错误：

我不确定是什么原因造成的，也许与 JQuery 有关？

这是确切的代码：

//when add to cart link is clicked...
$('.addtocart').on('click', function(){

  //get the value of the "data-value" attribute for that link
  var vehicleRegistration = $(this).data('value');
  //save it to localStorage
  localStorage.setItem('vehicleRegistration', vehicleRegistration);


  //read from localStorage
  if( localStorage.getItem('vehicleRegistration') ){
    //add the value to the form input
    $('#field34').val( localStorage.getItem('vehicleRegistration') );
  }

});

这是它发生的页面：http://drivencarsales.co.uk/book-testdrive http://drivencarsales.co.uk/book-testdrive

这真的让我很困惑，如果有人能帮助我解决这个问题，我将不胜感激。

谢谢，尼克

在您的网站中，您同时拥有prototype.js and jQuery添加。这$这里调用prototype.js代替jQuery。因此，请将其更改为：

jQuery('.addtocart').on('click', function(){

  //get the value of the "data-value" attribute for that link
  var vehicleRegistration = jQuery(this).data('value');
  //save it to localStorage
  localStorage.setItem('vehicleRegistration', vehicleRegistration);


  //read from localStorage
  if( localStorage.getItem('vehicleRegistration') ){
    //add the value to the form input
    jQuery('#field34').val( localStorage.getItem('vehicleRegistration') );
  }

});

或者你也可以这样做：

(function ($) {
    $('.addtocart').on('click', function(){

      //get the value of the "data-value" attribute for that link
      var vehicleRegistration = $(this).data('value');
      //save it to localStorage
      localStorage.setItem('vehicleRegistration', vehicleRegistration);


      //read from localStorage
      if( localStorage.getItem('vehicleRegistration') ){
        //add the value to the form input
        $('#field34').val( localStorage.getItem('vehicleRegistration') );
      }

    });
})(jQuery);