BookInstance detail page and challenge

BookInstance detail page

The BookInstance detail page needs to display the information for each BookInstance, identified using its (automatically generated) _id field value. This will include the Book name (as a link to the Book detail page) along with other information in the record.


Open /controllers/bookinstanceController.js. Find the exported bookinstance_detail() controller method and replace it with the following code.

// Display detail page for a specific BookInstance.
exports.bookinstance_detail = asyncHandler(async (req, res, next) => {
  const bookInstance = await BookInstance.findById(

  if (bookInstance === null) {
    // No results.
    const err = new Error("Book copy not found");
    err.status = 404;
    return next(err);

  res.render("bookinstance_detail", {
    title: "Book:",
    bookinstance: bookInstance,

The implementation is very similar to that used for the other model detail pages. The route controller function calls BookInstance.findById() with the ID of a specific book instance extracted from the URL (using the route), and accessed within the controller via the request parameters: It then calls populate() to get the details of the associated Book. If a matching BookInstance is not found an error is sent to the Express middleware. Otherwise the returned data is rendered using the bookinstance_detail.pug view.


Create /views/bookinstance_detail.pug and copy in the content below.

extends layout

block content

  h1 ID: #{bookinstance._id}

  p #[strong Title: ]
    a( #{}
  p #[strong Imprint:] #{bookinstance.imprint}

  p #[strong Status: ]
    if bookinstance.status=='Available'
      span.text-success #{bookinstance.status}
    else if bookinstance.status=='Maintenance'
      span.text-danger #{bookinstance.status}
      span.text-warning #{bookinstance.status}

  if bookinstance.status!='Available'
    p #[strong Due back:] #{bookinstance.due_back}

Everything in this template has been demonstrated in previous sections.

What does it look like?

Run the application and open your browser to http://localhost:3000/. Select the All book-instances link, then select one of the items. If everything is set up correctly, your site should look something like the following screenshot.

BookInstance Detail Page - Express Local Library site


Currently most dates displayed on the site use the default JavaScript format (e.g. Tue Oct 06 2020 15:49:58 GMT+1100 (AUS Eastern Daylight Time)). The challenge for this article is to improve the appearance of the date display for Author lifespan information (date of death/birth) and for BookInstance detail pages to use the format: Oct 6th, 2016.

Note: You can use the same approach as we used for the Book Instance List (adding the virtual property for the lifespan to the Author model and use luxon to format the date strings).

To complete this challenge, you must:

  1. Replace the variable due_back with due_back_formatted in the BookInstance detail page.
  2. Update the Author model to add a lifespan virtual property. The lifespan should look like: date_of_birth - date_of_death, where both values have the same date format as BookInstance.due_back_formatted.
  3. Use Author.lifespan in all views where you currently explicitly use date_of_birth and date_of_death.

Next steps