Express trigger not found route for each route - node.js

Question

I am using express with a pattern like this :
app = express();
router = express.Router();
router.use((req, res, next) => {
console.log("my middleware before");
next();
});
router.get('/foo', (req, res, next) => {
console.log("My route");
res.send("<h1>Hello</h1>")
next();
});
router.use((req, res, next) => {
console.log("my middleware after");
});
app.use("/", router);
app.get("*", (req, res, next) => {
console.log("page not found");
throw new Error("Not Found");
});
app.use((err, req, res, next) => {
console.log("Error occure");
res.send("<h1>Error</h1>");
});
app.listen(3000);
When I request '/foo' I would like to have
> my middleware before
> My route
> my middleware after
<h1>Hello</h1>
And when I request anything else :
> page not found
> Error occure
<h1>Error</h1>
But the page not found route is executed in each case, even if route '/foo' is done.
How can I get it working ?

Answer 1

When I run your code, I do not get the output you show, so something about your real code is apparently different than what you show in your question.
I do get a slightly confusing output and that happens because the browser sends both the /foo request and a /favicon.ico request. When I run it, the /foo request generates the desired output. The /favicon.ico request generates some middleware output and then gets stuck in the router.
If you filter out the /favicon.ico route (so that it doesn't confuse things) by adding this as the first route:
app.get("/favicon.ico", (req, res) => {
res.sendStatus(404);
});
Then, I get exactly this output in the server logs when I request /foo:
my middleware before
My route
my middleware after
Which is exactly what you asked for.
There is, however, a general problem with this:
router.use((req, res, next) => {
console.log("my middleware after");
});
Because it will catch and hang any legit requests that haven't yet had a response sent. You can't really code it that way unless you only don't call next() if a response has already been sent.
As a bit of a hack, you could do this:
router.use((req, res, next) => {
console.log("my middleware after");
// if response hasn't yet been sent, continue routing
if (!res.headersSent) {
next();
}
});
But, there is probably a better way to solve whatever problem you're actually trying to solve. If, in the future, you describe your real problem rather than a problem you have with your solution, then you allow people to offer a wider range of solutions to your real problem including things you haven't even thought of to try. As your question is written right now, we're stuck down the solution path you followed and don't know what the original problem was. That is, by the way, referred to as an XY Problem.

Answer 2

Do this
app = express();
router = express.Router();
router.use((req, res, next) => {
console.log("my middleware before");
next();
});
router.get('/foo', (req, res, next) => {
// use locals to record the fact we have a match
res.locals.hasMatch = true
console.log("My route");
res.send("<h1>Hello</h1>")
next();
});
router.use((req, res, next) => {
console.log("my middleware after");
});
app.use("/", router);
app.get("*", (req, res, next) => {
console.log("page not found");
throw new Error("Not Found");
});
app.use((err, req, res, next) => {
// check locals to see if we have a match
if (!res.locals.hasMatch) {
console.log("Error occure");
res.send("<h1>Error</h1>");
}
});
app.listen(3000);

Answer 3

You can utilize middlewares and even nest them.
You can implement it like this:
Middlewares
const before = (req, res, next) => {
console.log("my middleware before");
next(); // Supply next() so that it will proceed to the next call,
// in our case, since this is supplied inside the router /foo, after this runs, it will proceed to the next middleware
};
const after = (req, res, next) => {
console.log("my middleware after");
};
Route
// Supply "before" middleware on 2nd argument to run it first when this route is called
router.get('/foo', before, (req, res, next) => {
console.log("My route");
res.send("<h1>Hello</h1>");
next(); // Call next() to proceed to the next middleware, or in "after" middleware
}, after); // Supply the "after" middleware
Once ran, it will proceed with this desired result sequence:
> my middleware before
> My route
> my middleware after
Unmatched Routes Handler
Instead of this
app.get("*", (req, res, next) => {
console.log("page not found");
throw new Error("Not Found");
});
You can implement it like this instead, this is after your app.use("/", router); -- This will handle your unmatched routes:
Sources:
https://stackoverflow.com/a/44540743/6891406
https://stackoverflow.com/a/16637812/6891406
app.use((req, res, next) => {
console.log("page not found");
res.json({ error: 'Page not Found' })
});