Catch express bodyParser error

I want to catch the error from the bodyParser() middleware when I send a json object and it is invalid because I want to send a custom response instead of a generic 400 error.

This is what I have and it works:

app.use (express.bodyParser ());
app.use (function (error, req, res, next){
    //Catch bodyParser error
    if (error.message === "invalid json"){
        sendError (res, myCustomErrorMessage);
    }else{
        next ();
    }
});

But this seems to me a very ugly approach because I’m comparing the error message which could change in future express versions. There’s any other way to catch bodyParser() errors?

EDIT:

This is the error when the request body has an invalid json:

{
  stack: 'Error: invalid jsonn    at Object.exports.error (<path>/node_modules/express/node_modules/connect/lib/utils.js:55:13)n    at IncomingMessage.<anonymous> (<path>/node_modules/express/node_modules/connect/lib/middleware/json.js:74:71)n    at IncomingMessage.EventEmitter.emit (events.js:92:17)n    at _stream_readable.js:872:14n    at process._tickDomainCallback (node.js:459:13)',
  arguments: undefined,
  type: undefined,
  message: 'invalid json',
  status: 400
}

Pretty printed stack:

Error: invalid json
    at Object.exports.error (<path>/node_modules/express/node_modules/connect/lib/utils.js:55:13)
    at IncomingMessage.<anonymous> (<path>/node_modules/express/node_modules/connect/lib/middleware/json.js:74:71)
    at IncomingMessage.EventEmitter.emit (events.js:92:17)
    at _stream_readable.js:872:14
    at process._tickDomainCallback (node.js:459:13)

Answer

Ok, found it:

bodyParser() is a convenience function for json(), urlencoded() and multipart(). I just need to call to json(), catch the error and call to urlencoded() and multipart().

bodyParser source

app.use (express.json ());
app.use (function (error, req, res, next){
    //Catch json error
    sendError (res, myCustomErrorMessage);
});

app.use (express.urlencoded ());
app.use (express.multipart ());