What is it about the following javascript that returns 0, no matter the input entered into the field by the user?

I am using the input (Single Line) field. There are no other fields with this class name.

  $('.testclass').on('blur', 'input', customshowhide);

  
  function customshowhide() {
   
    var input = $('.testclass').val();
    alert(input);

  }