Getting 404 error on Delete Functionality on Express Article tutorial

I implemented Delete functionality form express article on MDN , following the " Delete Author " Article .
It gives 404 error (Not Found) .

Here is the code:

exports.author_delete_get = asyncHandler(async (req, res, next) => {

// Get details of author and all their books (in parallel)

const [author, allBooksByAuthor] = await Promise.all([

  Author.findById(req.params.id).exec(),

  Book.find({ author: req.params.id }, "title summary").exec(),

]);

console.log(author);



if (author === null) {

  // No results.

  res.redirect("/catalog/authors");

}



res.render("author_delete", {

  title: "Delete Author",

  author: author,

  author_books: allBooksByAuthor,

 

});

});

// Handle Author delete on POST

/*

exports.author_delete_post = asyncHandler(async (req,res,next)=>{

// res.send("NOT IMPLEMENTED: Author delete POSt");

// Get details of author and their books (in parallel).

const [author, allBooksByAuthor] = await Promise.all([

    Author.findById(req.params.id).exec(),

    Book.find( {author: req.params.id}, "title summary").exec(),

]);

if(allBooksByAuthor.length>0) {

     //  Author has books. Render in same way as for GET route

     res.render("author_delete", {

         title: "Delete Author",

         author: author,

         author_books: allBooksByAuthor,

     });

     return;

}

else {

    // Author has no books . Delete object and redirect to the list of authors.

    await Author.findByIdAndDelete(req.body.author.id);

    res.redirect("/catalog/authors");

}

});

*/

exports.author_delete_post = asyncHandler(async (req, res, next) => {

// Get details of author and all their books (in parallel)

const [author, allBooksByAuthor] = await Promise.all([

  Author.findById(req.params.id).exec(),

  Book.find({ author: req.params.id }, "title summary").exec(),

]);



if (allBooksByAuthor.length > 0) {

  // Author has books. Render in same way as for GET route.

  res.render("author_delete", {

    title: "Delete Author",

    author: author,

    author_books: allBooksByAuthor,

    action: mongoDB,

  });

  return;

} else {

  // Author has no books. Delete object and redirect to the list of authors.

  await Author.findByIdAndDelete(req.body.author_.id);

  res.redirect("/catalog/authors");

}

});

PUG template code :

extends layout

block content

h1 #{title}: #{author.name}

p= author.lifespan

if author_books.length

p #[strong Delete the following books before attempting to delete this author.]

div(style='margin-left:20px;margin-top:20px')

  h4 Books

  dl

  each book in author_books

    dt

      a(href=book.url) #{book.title}

    dd #{book.summary}

else

p Do you really want to delete this Author?

form(method='POST' action='')

  div.form-group

    input#authorid.form-control(type='hidden',name='authorid', required='true', value=author._id )

  button.btn.btn-primary(type='submit') Delete