BookInstance list page

The BookInstance list controller function needs to get a list of all book instances, populate the associated book information, and then pass the list to the template for rendering.

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

// Display list of all BookInstances.
exports.bookinstance_list = asyncHandler(async (req, res, next) => {
  const allBookInstances = await BookInstance.find().populate("book").exec();

  res.render("bookinstance_list", {
    title: "Book Instance List",
    bookinstance_list: allBookInstances,
  });
});

The route handler calls the find() function on the BookInstance model, and then daisy-chains a call to populate() with the book field—this will replace the book id stored for each BookInstance with a full Book document. exec() is then daisy-chained on the end in order to execute the query and return a promise.

The route handler uses await to wait on the promise, pausing execution until it is settled. If the promise is fulfilled, the results of the query are saved to the allBookInstances variable, and the route handler continues execution.

The last part of the code calls render(), specifying the bookinstance_list (.pug) template and passing values for the title and bookinstance_list into the template.

Create /views/bookinstance_list.pug and copy in the text below.

extends layout

block content
  h1= title

  ul
    each val in bookinstance_list
      li
        a(href=val.url) #{val.book.title} : #{val.imprint} -
        if val.status=='Available'
          span.text-success #{val.status}
        else if val.status=='Maintenance'
          span.text-danger #{val.status}
        else
          span.text-warning #{val.status}
        if val.status!='Available'
          span  (Due: #{val.due_back} )

    else
      li There are no book copies in this library.

This view is much the same as all the others. It extends the layout, replacing the content block, displays the title passed in from the controller, and iterates through all the book copies in bookinstance_list. For each copy we display its status (color coded) and if the book is not available, its expected return date. One new feature is introduced—we can use dot notation after a tag to assign a class. So span.text-success will be compiled to <span class="text-success"> (and might also be written in Pug as span(class="text-success").

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

• Return to Express Tutorial Part 5: Displaying library data.
• Proceed to the next subarticle of part 5: Date formatting using luxon.