Express Before Next

Combining several Express apps and routers together is useful, but often changes to the request and response are leaked down the router chain. This plugin provides a small API for cleaning up when the next() method is called on the router.

Install

npm install express-before-next

Usage

Call attachBeforeNext(router) on any Express Router or Application instance. This will monkey patch the .handle() method on these objects. A req.beforeNext() is attached to the request, pass it functions to be called on clean up. Keep in mind this method are only called if next is called.

const express = require("express");
const attachBeforeNext = require("express-before-next");

function createHomeRoute() {
  const router = express();

  // monkey patch this router
  attachBeforeNext(router);

  router.use(function(req, res, next) {
    // set state on the request that should be cleaned up
    res.locals.foo = "bar";

    // clean up state before going to the next router
    req.beforeNext(() => {
      delete res.locals.foo;
    });
  });

  router.get("/", function(req, res) {
    res.render("home");
  });

  return router;
}

const bigapp = express();
bigapp.use(createHomeRouter());

// when these routes get called, res.locals won't bleed in from above
bigapp.use(otherRoutes());