How can I prevent express js server from crashing when error occurs?

Question

If I send a valid fetch api query to this Express server it works fine. If I send an invalid query the server crashes (ReferenceError: next is not defined). How can I change this so that if an error occurs;

the server does not crash
the client receives an error message from the server

Express server.js:

// Add a new test-resource-a
app.post('/test-resource-a', (request, response) => {
    pool.query('INSERT INTO my_table SET ?', request.body, (error, result) => {
        if (error) {
            next(err);
        }
        response.status(201).send(`test-resource-a added with id: ${result.insertId}`);
    });
});

//An error handling middleware
app.use(function (err, req, res, next) {
    res.status(500);
    res.send("Oops, something went wrong.")
});

manlok manlok · Accepted Answer · 2019-04-21 11:26:01Z

1

This error is mean the next method is not define. In your case, I think you don't need the next method.

// Add a new test-resource-a
app.post('/test-resource-a', (request, response) => {
    pool.query('INSERT INTO my_table SET ?', request.body, (error, result) => {
        if (error) {
            response.status(400).send(err);
        } else {
            response.status(201).send(`test-resource-a added with id: ${result.insertId}`);
        }
    });
});

//An error handling middleware
app.use(function (err, req, res, next) {
    res.status(500);
    res.send("Oops, something went wrong.")
});

edited Apr 21, 2019 at 11:26

answered Apr 21, 2019 at 11:13

manlok manlok

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2 Comments

Fred Over a year ago

Thanks Manlok - works great! (err should be error but I ended upp changing it to 'There was an error' to avoid sending sensitive db info to the client). Not sure what the 'middleware' is needed for so I removed it. I suppose that like this all errors will be shown as '400 (Bad Request)'? What if I want to give more detailed error messages to the client - do I just add an if/else statement in the same place with different error messages?

manlok manlok Over a year ago

you can revise your query to check more condition.

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