[hombre_fatal]

One example would be a url router for a web server that turns the url variables into the handler's expected argument type and ignores requests that do not.

    router.get('/users/:id', (id: UUID) => ...)
    router.get('/products/:id', (id: Int) => ...)

[tracker1]

That would be relatively easy to do something very similar with middleware for express/koa

    router.get('/users/:id'. skipNonUuid(id => ...))

You simply have a function/middleware that does the check.... or `compose(skipNonUuid, dbo.findUserById, ui.formatView('modelName'))`

You can do function composition that is nearly as simple and far more flexible in general with JS