In Rails, how do I query my database from JavaScript so I can save the value of the query?

Question

I would like to make a query given the id of my book in javascript and not fetch all the books from the database, for example:

I usually do it like this:

In my book controller , I make a query the collection of books and then pass it to the view through a variable:

# books_controllers.rb
before_action :set_books
... 
def set_books
  @books = Book.all # here is my books collection
end

In my form view I define a variable to store the collection of books, in a books_info variable:

#books/form
javascript:
   let books_info = #{@books.to_json.html_safe};

And finally, the collection of books is scanned and compared with the id that the client gives me to find the specific information of said book.

    Array.from(books_info).forEach((element, index) => {
      if (element["book_id"] === client_book_id){
        new_book_id = element;
      }
    });

The problem with doing all that is that I compromise all the book information in views

Simply what I am looking for is given the id of the client ( client_book_id ) to do this in javascript

javascript:
  let client_book_id = #{Book.find(´client_book_id´).to_json.html_safe} # This not work but I try to got it.

If you could help me I would be very grateful.

Answer 1

1. Add the book ID to the query string of the URL, eg ?book_id=123
2. The Rails controller reads the ID as eg params[:book_id]
3. The controller sets an instance variable , eg @book = Book.find(params[:book_id])
4. The Rails view sets the JS variable using .to_json as already shown in the question

This is just one application design, good for beginners. Other designs include XHR (intermediate) or GraphQL (advanced).