code: function on (route, methods) {
      assert.equal(typeof route, 'string')
      methods = methods || {}
  
      // mount subrouter
      if (methods[sym]) return router.on(route, methods)
  
      assert.equal(typeof methods, 'object')
  
      // mount http methods
      router.on(route, function (args) {
        demuxSsa(args, function (req, res, params) {
          const meth = methodist(req, defaultFn, methods)
          meth(req, res, params)
  
          // default function to call if methods don't match
          // null -> null
          function defaultFn () {
            router._default(args)
          }
        })
      })
      return emit
    }
docs: register a new route on a method (str, obj) -> obj