Generic compose

[xgbuils]

Hi @blakeembrey

During the implementation, I noticed that Express app.use and app[METHOD] accepts variadic number of middlewares implementing internally the composition as @knksmith57 expected in #4

However having this implementation is useful for having same behaviour as express in other server libraries like connect.

Cheers!

[coveralls]

Coverage increased (+1.4%) to 94.097% when pulling c1743535fd3ab42baecc8d488e227df7036d045a on xgbuils:generic-compose into a379394f76deb213a631bbc0a7e195c2ea5b3908 on blakeembrey:master.

[coveralls]

Coverage increased (+1.4%) to 94.097% when pulling c1743535fd3ab42baecc8d488e227df7036d045a on xgbuils:generic-compose into a379394f76deb213a631bbc0a7e195c2ea5b3908 on blakeembrey:master.

[xgbuils]

@blakeembrey

Another quirky feature that's may be semi-useful is that arrays are mutable whereas arguments are not -this could be a reason to accept an array instead of an arguments list in cases where someone may want to mutate middleware in the future.

Could you give a use case about mutating the array and then using it?

Thanks!

[blakeembrey]

Could you give a use case about mutating the array and then using it?

const arr = []

const handler = compose(arr)

// Some time later...
arr.pop()
arr.push(() => 'blah')

Not saying it's a particularly good practice, but it is something possible we support an array only.

[xgbuils]

Hi @blakeembrey

I was asking about a real use case because I think we don't need to implement solution that no one is using. For example I'm tried to implement a case where the words of the response rotates after each request trying to use array mutation:

First response after first request:

this is a mutable example 

Second response after second request:

is a mutable example this 

Third response after third request:

a mutable example this is 

However, I was not able to get a solution with the current versions of express and compose-middleware libraries:

const express = require('express');
const app = express();
const { compose } = require('compose-middleware');

const middlewares = [
    (req, res, next) => {
        res.write('this ');
        next();
    },
    (req, res, next) => {
        res.write('is ');
        next();
    },
    (req, res, next) => {
        res.write('a ');
        next();
    },
    (req, res, next) => {
        res.write('mutable ');
        next();
    },
    (req, res, next) => {
        res.write('example ');
        next();
    }
];

app.get('/', compose(middlewares));
app.use('/', (req, res, next) => {
    middlewares.push(middlewares.shift());
    console.log(middlewares.map(f => f.toString()))
    console.log('\n')
    res.end()
    next();
})

app.listen(3000, function () {
  console.log('Example app listening on port 3000!');
});

Then, do you have a real example where array mutation is applicable and useful?

Thanks!