Menu
Express by default returns errors as HTML pages. As I'm developing a REST api, I want all my errors to be in JSON format. How can i configure express for this?
I expect the response to look something like this
{ "statusCode": 404, "error": "Not Found" } but instead I get
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <title>Error</title> </head> <body> <pre>Cannot DELETE /object/</pre> </body> </html> This is my basic app
export const app = express(); app.use(express.json()); app.get("/objects", listObjects); app.get("/object/:id", getObject); app.post("/object", createObject); app.put("/object/:id", updateObject); app.delete("/object/:id", deleteObject); UPDATE: To clarify, it is not the errors from my handlers I want to handle as json. Doing that is pretty straight forward.
What I'm after is for express to stop returning html errors for unregistered handlers, like doing DELETE on /assessments, or GET on /anUnknownRoute
957
By default, you won't be able to parse JSON from the body of an incoming request with Express.
The JSON. stringify() is the inbuilt method in nodejs it accepts a javascript object and returns the stringified object. The call to end() function indicates to the server that all processes have been finished so that it can send the response to the user.
json() Function. The res. json() function sends a JSON response. This method sends a response (with the correct content-type) that is the parameter converted to a JSON string using the JSON.
json() is a built-in middleware function in Express. This method is used to parse the incoming requests with JSON payloads and is based upon the bodyparser. This method returns the middleware that only parses JSON and only looks at the requests where the content-type header matches the type option.
You add custom error handling middleware - which is regular middleware but with 4 arguments instead of 3 - to the middleware stack. In this error handler you use res.status(code).send(jsonResponse) to send the json error.
A simple quick example that will always send status 500 JSON errors:
const bodyParser = require('body-parser') const express = require('express') const jsonErrorHandler = async (err, req, res, next) => { res.status(500).send({ error: err }); } const app = express() // The other middleware app.use(bodyParser.json()) // Your handler app.use(jsonErrorHandler) You may simply add 'Content-Type: application/json' to your response headers and write basically anything you want in JSON format, e.g.
function(err, req, res, next){ res.setHeader('Content-Type', 'application/json'); res.status(500); res.send(JSON.stringify(error)); }); Or you can use res.json instead. Please, see official doc for more detailed information: https://expressjs.com/en/api.html#res.json
If you want to return errors in JSON by default, then you may be interested in using default express error-handling mechanism: https://expressjs.com/en/guide/error-handling.html
Just pass an error to the next callback to go straight to the error-handler (skipping everything else in the queue in between) and add an error-handling middleware to the end of your middleware queue. This should do the trick.
P.S. From express.js FAQ:
In Express, 404 responses are not the result of an error, so the error-handler middleware will not capture them. This behavior is because a 404 response simply indicates the absence of additional work to do; in other words, Express has executed all middleware functions and routes, and found that none of them responded. All you need to do is add a middleware function at the very bottom of the stack (below all other functions) to handle a 404 response:
app.use(function (req, res, next) { res.status(404).send("Sorry can't find that!") }) Obviously, you may send a response in JSON format...
41
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
