Middleware getting called for error handling but not handling response
Question
I am trying to handle errors by returning json, but my error handler (while being called, logs in console) wont return what I am trying to return. Here is the handler:
const handleError = function(err, req, res, next) {
console.log(err);
res.setHeader('Content-Type', 'application/json');
res.status(500);
res.send(JSON.stringify(error));
}
But I get returned a render function that translate to the following returned to me as the user:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Error</title>
</head>
<body>
<pre>Invalid token with reason JsonWebTokenError: jwt malformed</pre>
</body>
</html>
So it will still log the error but unless I return an error in my actual function it wont return as intended, aka the following function does return a json error as written:
const view = function(req, res, model, settings = {}, callback) {
let { params } = req;
let { _id } = params;
let { select, limit, sort } = settings;
let query = model.findById(_id);
if (select) query.select(select);
if (sort) query.sort(sort);
if (limit) query.limit(limit);
query.exec(function(err, data) {
if(callback) {
callback(err,data);
}else{
if (err) return res.status(400).json({ 'Error': err.message });
if (!data) return res.status(404).json({ 'Error': `No document with id ${_id} found` });
return res.status(200).json(data);
}
});
}
Here is how I register my middlewares
let app = express();
app.server = http.createServer(app);
// logger
app.use(morgan('dev'));
// 3rd party middleware
app.use(cors({
exposedHeaders: config.corsHeaders
}));
// Custom error handling
app.use(api.handleError);
//Set body as json as recieved
app.use(bodyParser.json({
limit : config.bodyLimit
}));
3 answers
solution1
0 2019-05-09 01:18:03
When I read the express documentation on error handling, it seems to me like you're supposed to throw new Error() (or call next() , depending on the sync/async nature of your handlers) in order to get the error handler working.
In your code above, I see you return res.status().json() -- which I don't think is the same thing.
You've pointed out that unless I return an error in my actual function, it won't return as intended -- so it sounds like you already know what's happening.
You also mentioned that handleError should return JSON -- why not change this:
res.status(500);
res.send(JSON.stringify(error));
...to...
res.status(500).json(error)
That should give you what you need.
solution2
0 2019-05-09 03:35:50
Try to add error handler middleware bellow your route. Example:
app.get('/', indexHandler)
//call next(err) in indexHandler if there is an error
app.use(errorHandler)
solution3
0 2022-05-22 23:38:26
The answer is very simple install express-async-errors https://www.npmjs.com/package/express-async-errors
run npm install express-async-errors
and require it at the top of your app.js file
require('express-async-errors')
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