njseries_02_05.js

router.get('/chain/example', [ 
            (req, res, next) => {
                req.chain = 'one ->'
                next()
            }, 
            (req, res, next) => {
                req.chain = `${ req.chain} two ->`
                next()
            }, 
            (req, res, next) => {
                res.end(`${req.chain} three`)
                // next -> udefined thus cannot be called
            }
        ]
    )