Delete a record from database using node.js/Express.js

[abbe]

I have been sitting with this project for 2 days and couldn’t figure out what is wrong. I Will be grateful if u could help me point out the problem

• I want to delete a record from the HTML table. I can retrieve the book_id, how can I access the book_id in my delete function.

<script>
            fetch('http://localhost:3003/booked').then(function (response) {
                return response.json();
            }).then(function (data) {
                appendData(data);
            }).catch(function (err) {
                console.log("error:" + err);
            });
            function appendData(data) {
                let tbodyContainer = document.getElementById("tbody");
                for (let i = 0; i < data.length; i++) {
                    let tr = document.createElement("tr");
                    tr.innerHTML =
                        "<tr>"
                        +
                        "<th>" + data[i].book_id + "</th>" +
                        "<th>" + data[i].descr + "</th>" +
                        "<th>" + data[i].book_date + "</th>" +
                        `<th> <a href='/booked/${data[i].book_id}'>Cancel</a></th>` +
                        "</tr>";
                    tbodyContainer.appendChild(tr);
                }
            }
        </script>

• How can I retrieve the book_id from the HTML table and pass it to the delete function below, so that I can compare the book_id and delete that record. When I console.log the book_id, it returns undefined

app.delete("/booked/:book_id", (req, res) => {
    const book_id = req.params.book_id;
    console.log("--------------> " + book_id); 
    if (!req.session.loggedin) {
        return res.status(401).redirect("./login");
    } else {
        connection.query("DELETE FROM calendar.book WHERE book_id= '" + book_id + "'", function (err, result) {
            if (err) {
                throw err;
            } else {
               res.redirect("./myBookings");
            }
        });
    }
});

[caryaharper]

Check typeof book_id because I would not be to surprised if the original id is an object. When you grab the id from your params you are getting a string but the original id may in fact not be a string. What sort of database are you working with?

[abbe]

I’ve finally solved the problem, and this is how I’ve solved it. After a few days of trying to figure it out, I read the documentation about req. query, and changed the delete route to
<th> <a href='/delete?book_id=${data[i].book_id}'>Cancel</a></th>

fetch('http://localhost:3003/booked').then(function (response) {
                return response.json();
            }).then(function (data) {
                appendData(data);
            }).catch(function (err) {
                console.log("error:" + err);
            });
            function appendData(data) {
                let tbodyContainer = document.getElementById("tbody");
                for (let i = 0; i < data.length; i++) {
                    let tr = document.createElement("tr");
                    tr.innerHTML =
                        "<tr>"
                        +
                        "<th>" + data[i].book_id + "</th>" +
                        "<th>" + data[i].descr + "</th>" +
                        "<th>" + data[i].book_date + "</th>" +
                        `<th> <a href='/booked/${data[i].book_id}'>Cancel</a></th>` +
                        "</tr>";
                    tbodyContainer.appendChild(tr);
                }
            }
 </script>

And inside the delete express route, I’ve changed the
req.params.book_id to req.query.book_id, and changed the MySQL query (just removed the quotes ( ' ') in between the book_id)
Below is the full code of the delete route.

app.get("/delete", (req, res) => {
    const book_id = req.query.book_id;
    console.log("--------------> " + book_id); //<------------------------------
    if (!req.session.loggedin) {
        return res.status(401).redirect("./login");
    } else {
        connection.query("DELETE FROM calendar.book WHERE book_id= " + req.query.book_id, function (err, result) {
           if (err) {
                throw err;
            } else {
                res.redirect("./myBookings");
            }
        });
    }
});

NOTE - This may not be the best solution out there, I am just a newbie