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Since v5 relies on node >= 18, this is now possible (since v16, v14.18.0 [^1][^2]). It's functionally irrelevant: 1. It's not required for CJS nor ESM (with a few exceptions [^3]) 2. It has no performance promises However, there are upsides to this approach: 1. It brings clear boundaries to what's a built-in and what's an external dependency 2. It reduces the risk of importing unwanted deps where a built-in is expected 3. It's slightly more interoperable with other JS runtimes that provide node compatibility[^4], albeit only during development. Once imported from npm, built-ins are assumed. [^1]:https://nodejs.org/docs/latest-v22.x/api/modules.html#built-in-modules [^2]:https://github.com/nodejs/node/pull/37246 [^3]:https://nodejs.org/api/modules.html#built-in-modules-with-mandatory-node-prefix [^4]:https://docs.deno.com/runtime/fundamentals/node/#using-node's-built-in-modules
156 lines
3.1 KiB
JavaScript
156 lines
3.1 KiB
JavaScript
'use strict'
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/**
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* Module dependencies.
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*/
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var express = require('../..');
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var path = require('node:path');
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var User = require('./user');
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var app = express();
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app.set('views', path.join(__dirname, 'views'));
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app.set('view engine', 'ejs');
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// filter ferrets only
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function ferrets(user) {
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return user.species === 'ferret'
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}
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// naive nesting approach,
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// delegating errors to next(err)
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// in order to expose the "count"
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// and "users" locals
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app.get('/', function(req, res, next){
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User.count(function(err, count){
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if (err) return next(err);
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User.all(function(err, users){
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if (err) return next(err);
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res.render('index', {
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title: 'Users',
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count: count,
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users: users.filter(ferrets)
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});
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})
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})
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});
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// this approach is cleaner,
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// less nesting and we have
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// the variables available
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// on the request object
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function count(req, res, next) {
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User.count(function(err, count){
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if (err) return next(err);
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req.count = count;
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next();
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})
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}
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function users(req, res, next) {
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User.all(function(err, users){
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if (err) return next(err);
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req.users = users;
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next();
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})
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}
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app.get('/middleware', count, users, function (req, res) {
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res.render('index', {
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title: 'Users',
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count: req.count,
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users: req.users.filter(ferrets)
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});
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});
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// this approach is much like the last
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// however we're explicitly exposing
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// the locals within each middleware
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//
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// note that this may not always work
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// well, for example here we filter
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// the users in the middleware, which
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// may not be ideal for our application.
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// so in that sense the previous example
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// is more flexible with `req.users`.
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function count2(req, res, next) {
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User.count(function(err, count){
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if (err) return next(err);
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res.locals.count = count;
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next();
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})
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}
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function users2(req, res, next) {
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User.all(function(err, users){
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if (err) return next(err);
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res.locals.users = users.filter(ferrets);
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next();
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})
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}
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app.get('/middleware-locals', count2, users2, function (req, res) {
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// you can see now how we have much less
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// to pass to res.render(). If we have
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// several routes related to users this
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// can be a great productivity booster
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res.render('index', { title: 'Users' });
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});
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// keep in mind that middleware may be placed anywhere
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// and in various combinations, so if you have locals
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// that you wish to make available to all subsequent
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// middleware/routes you can do something like this:
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/*
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app.use(function(req, res, next){
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res.locals.user = req.user;
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res.locals.sess = req.session;
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next();
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});
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*/
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// or suppose you have some /admin
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// "global" local variables:
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/*
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app.use('/api', function(req, res, next){
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res.locals.user = req.user;
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res.locals.sess = req.session;
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next();
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});
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*/
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// the following is effectively the same,
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// but uses a route instead:
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/*
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app.all('/api/*', function(req, res, next){
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res.locals.user = req.user;
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res.locals.sess = req.session;
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next();
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});
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*/
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/* istanbul ignore next */
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if (!module.parent) {
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app.listen(3000);
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console.log('Express started on port 3000');
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}
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