CODEWITHSUNDEEP
node.jsexpress
Troy
Troy

Reputation: 1839

Node.js w/ express error handling in callback

I'm new to node.js and express. I have the following in my app.js file as a last resort error handler:

app.use(function(err, req, res, next){
  // we may use properties of the error object
  // here and next(err) appropriately, or if
  // we possibly recovered from the error, simply next().
  res.status(err.status || 500);

  console.log(err);

  var errMsg = "An internal error occurred. Please notify your system administrator.";

  // respond with json
  if (req.accepts('json')) {
    res.send({error: errMsg});
    return;
  }

  // respond with html page
  if (req.accepts('html')) {
    res.render('500', errMsg);
    return;
  }

  res.type('txt').send(errMsg);
});

It works for me during testing when I kill the database server or otherwise induce a 'middleware' level error, but I'm not sure if it will also kick in when a callback receives an error? I've been using something like this inside my callbacks:

if(err) {
    console.log(err);
    res.send(500, {error: err});
}

but I'd like to better adhere to the DRY principle and figure out a way to handle errors inside callbacks globally (across modules) instead of writing a bunch of the same code. If the middleware 'catchall' won't work, am I stuck with a global function per module? Hope this make sense.

Upvotes: 4

Views: 1864

Answers (2)

Troy
Troy

Reputation: 1839

For now I ended up just creating a global error handler module:

exports.globalErrorHandler = function(err, req, res) {
  if(!err || !req || !res) return;

  console.log(err);

  var errMsg = "An internal error occurred. Please notify your system administrator.";

  // respond with json
  if (req.accepts('json')) {
    res.send({error: errMsg});
    return;
  }

  // respond with html page
  if (req.accepts('html')) {
    res.render('500', errMsg);
    return;
  }

  res.type('txt').send(errMsg);
}

and requiring it in the modules that need it:

var gh = require('../helpers/globalErrorHandler.js');

// Inside a callback
if(err) {
    gh.globalErrorHandler(err, req, res);
    return;
}

Upvotes: 1

Vadim Baryshev
Vadim Baryshev

Reputation: 26179

Look at connect-domain middleware. It helps you to catch all errors inside of asynchronous callbacks, timeouts, etc. Works only with node > 0.8.0.

Upvotes: 1

Related Questions