How can I catch errors in a JSON post in express.js

Question

I am creating an API in express.js where by the user posts JSON.

I've set the content type to application/json in the clients request. If I post valid JSON, all is well. However, posintg malformed JSON results in express throwing the following error...

string(370) "SyntaxError: Unexpected token } at Object.parse (native) at IncomingMessage. (/var/www/vhost/rest-v1/node/node_modules/express/node_modules/connect/lib/middleware/json.js:76:27) at IncomingMessage.EventEmitter.emit (events.js:92:17) at _stream_readable.js:910:16 at process._tickCallback (node.js:415:13)"

How can I catch this error so that I can respond with a more meaningful error message to the user?

Dan Kohn · Accepted Answer · 2013-07-26 10:39:52Z

1

User Express's built in error handling middleware or override it with your own: http://expressjs.com/guide.html#error-handling

answered Jul 26, 2013 at 10:39

Dan Kohn

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2 Comments

thomas-peter Over a year ago

Thanks for that. I have since found this, but I would like to handle the error differently for each route. I'm left wondering whether I need to ask another question. Is there a way of of disabling the automatic JSON parsing so that I cat do it within the route function?

Dan Kohn Over a year ago

The Express middleware that is parsing the JSON is called via bodyParser expressjs.com/api.html#middleware . Remove that middleware and you can instead parse it yourself in the route. However, I would recommend sticking with automatic parsing and just returning a 400 Bad Request HTTP response. Trying to deal intelligently with malformed JSON is both infinitely complex and a potential security hole.

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