Fixed Exercise 2 Part 2 addBook function

Exercise 2 Part 2 addBook function corrected to 

$("#addBook div").children("input").each(function(i, el){
          formData[el.id] = $(el).val();
});

original exercise code did not work as:

$("#addBook").children("input").each(function(i, el){
          formData[el.id] = $(el).val();
 });