Catch MySQL error when record does not exist in NodeJS

Question

I am trying to figure out how I can catch an error when a requested id is not found in the Database records.

My code is:

router.get('/users/:id', function(req, res) {

    getId = req.params.id

    db.con.query('SELECT * FROM employees where id=?', getId, function(err, results) {

       if (err) {
            console.log('error in query')
            return

        } else {
            obj = {
                id: results[0].id,
                name: results[0].name,
                location: results[0].location
                // error should be cached here when a requested results[0].id is not found
            }
            res.render('showuser');
        }
    })

});

In the console, I get the following error when a non-existed id is requested as it should be, however I cannot catch this error programmatically.

throw err; // Rethrow non-MySQL errors
^
ReferenceError: id is not defined
at Query._callback (C:\NodeJS\CRUD\CRUD-4\routes\add.js:21:13)

Node: v8.8.0

Express: v4.15.5

try printing the id using console.log(req.params.id) which will help you to see if the id is defined or not... plus initialize your getId variable var getId. add ; at the end of the statement. — jatinder bhola
– jatinder bhola, Commented Dec 7, 2017 at 18:56

Chris Thompson · Accepted Answer · 2017-12-07 18:52:40Z

2

Try this:

try{
  obj = {
     id: results[0].id,
     name: results[0].name,
     location: results[0].location
  }
}catch(err){
  //handle error
}

try {...}catch... is how you handle exceptions in JavaScript. You can read more about it here.

answered Dec 7, 2017 at 18:52

Chris Thompson

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Aikon Mogwai · Accepted Answer · 2017-12-07 18:59:41Z

1

// Error handler
app.use(function(err, req, res, next) {
  res.status(500).end(err.message);
}); 
...
router.get('/users/:id(\\d+)', function(req, res, next) {
    var id = req.params.id;

    db.con.query('SELECT * FROM employees where id= ?', id, function (err, results) {
       if (err) 
          return next(err);

       if (results.length == 0)
          return next(new Error('Incorrect id: ' + id));

        obj = {
            id: results[0].id,
            name: results[0].name,
            location: results[0].location
        }
        res.render('showuser', obj);
    });
})

answered Dec 7, 2017 at 18:59

Aikon Mogwai

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2 Comments

Cadmos Over a year ago

What does (\\d+) stand for in router.get ?

Chris Thompson Over a year ago

@Cadmos it means :id must be a number (\d) and it's length must be greater than 0 (+)

Hoang Long · Accepted Answer · 2022-09-06 15:53:28Z

1

Try the code below:

router.get('/product/:id', function(req, res, next){
        try {
            const { idProduct } = req.body
            const [detailProduct] = await Product.detail(idProduct);
            if (detailProduct.length === 0) {
                return res.status(404).send({
                    status: "404",
                    msg: "Not found",
                    data: null
                });
            }
            return res.status(200).json(detailProduct[0])
        } catch (error) {
            if (!error.statusCode) {
                error.statusCode = 500
            }
            next(error)
        }
    }

answered Sep 6, 2022 at 15:53

Hoang Long

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