Express.js ignore SyntaxError in case of unknown route - node.js

Question

In the express app below:
Executing a POST for /push with invalid json data will cause an HTTP 400 error to be sent back to the client
Executing a POST with valid json data, but for an unknown route will cause an HTTP 404 error to be sent back to the client
Executing a POST with invalid json data for an unknown route, will cause an HTTP 400 error to be sent back to the client
What I'd like to achieve, is that in the third scenario, also the 404 would be sent. In other words, in case the route is unknown, I want that to be catched by app.post('*',(req, res, next)), which will throw the 404, and not by the generic middleware error handler, which throws a 400 json SyntaxError
Any way to achieve this?
const express = require('express');
const { handleError, ErrorHandler } = require('./helpers/error');
const app = express();
app.use(express.json());
app.use(express.urlencoded({extended: true}));
app.get('/', function(req, res){
res.send('Hello World');
});
app.post('/', function(req, res){
console.log(req.body.data);
res.sendStatus(200);
});
app.post('/push', function(req, res){
console.log('push API');
res.sendStatus(200);
});
app.post('*',(req, res, next) => {
console.log('Unknown route');
throw new ErrorHandler(404, 'API endpoint does not exist.');
});
app.use((err, req, res, next) => {
console.log('Middleware error handling');
handleError(err, res);
});
app.listen(3000, function(){
console.log('Server started on port 3000')
});
error.js content:
class ErrorHandler extends Error {
constructor(statusCode, message) {
super();
this.statusCode = statusCode;
this.message = message;
}
}
const handleError = (err, res) => {
const { statusCode, message } = err;
res.status(statusCode).json({
status: "error",
statusCode,
message
});
};
module.exports = {
ErrorHandler,
handleError
}

Answer 1

By sending a request to a non-existing route, none of your handlers are matched. Thus, your error handling middleware
app.use((err, req, res, next) => {
console.log('Middleware error handling');
handleError(err, res);
});
is executed directly. What you can do is to try to detect a Syntax/parsing error in your handleError function. Something like:
const handleError = (err, res) => {
let {statusCode, message} = err;
if (err.status === 400 && err.message.includes("Unexpected token")) {
statusCode = 404;
}
res.status(statusCode).json({
status: "error",
statusCode,
message
});
};
EDIT:
The issue can be fixed by only using the json-parser middleware for the routes you want to parse json and removing it as a general middleware for all requests:
...
//app.use(express.json());
app.use(express.urlencoded({extended: true}));
app.post('/', express.json(), function (req, res) {
console.log(req.body.data);
res.sendStatus(200);
});
app.post('/push', express.json(), function (req, res) {
console.log('push API');
res.sendStatus(200);
});