lib/router.js
function (req, res, next) {
                    req.mounted = true
                    req.url     = req.url.replace(remove, '')

                    // clear cached req.path
                    delete req._path
                    delete req._pathLength

                    next()
                }
function (req, res, next) {
                    req.mounted = true
                    req.url     = req.url.replace(remove, '')

                    // clear cached req.path
                    delete req._path
                    delete req._pathLength

                    next()
                }
function ( req , res , next ) { req . mounted = true req . url = req . url . replace ( remove , '' ) // clear cached req.path delete req . _path delete req . _pathLength next ( ) }
add mount middleware to the beginning of this sub-chain
add mount middleware to the beginning of this sub - chain