Document customizing `express.json()` size limit for specific routes

[karlhorky]

In the following issue, it is requested to customize the body size limit for express.json() dynamically based on the API route:

@marbuser (Apr 11, 2019):
I've got some endpoints and 90% of them I want to have a limit of around '2MB'. However, there is 1 specific route, my upload route, where I want to have an upload limit of '10MB'.

• How to change the express.json limit option based on the route. express#3932

There are some solutions provided in the thread, but maybe a simpler option would be this one inspired by this Stack Overflow answer:

// Parse application/json
// - limit on /upload: 5MB
// - limit on other routes: default of 100KB
app.use('/upload', express.json({ limit: '5mb' }));
app.use(/^(?!\/upload$)/, express.json());

This may be a nice example to document on the express.json() docs section

[itsalb3rt]

For future people here, I have a problem because I forgot my pre-fix API structure, all my endpoints start with API

for example api/upload/

import bodyParser from 'body-parser';
// others imports

// more code...
app.use('/api/posts',bodyParser.json({ limit: '50mb' }));
app.use(/^(?!\/api\/\/posts$)/, bodyParser.json());

[jonchurch]

The root issue expressjs/express#3932 that inspired this issue is really about understanding middleware ordering and targeting specific routes with specific middleware, not about bodyParser.limit setting really.

[karlhorky]

@jonchurch hmm not sure what you mean.

I understood expressjs/express#3932 to be about "how can I configure the /upload route with a certain limit and non-/upload routes with a different limit?" since that is the case provided in that issue description at the top of the page.

I think my issue #1421 doesn't subvert that original wish.

Do you disagree with either of those things?