javascript 52 lines · 10 steps

Versioning an API with Express Routers

Two independent Express Routers hold v1 and v2 handlers, then mount under a parent router for clean URL versioning.

Explained by highlit
Express Intermediate api versioning routing modularity error handling pagination
1const express = require('express');
2 
3const v1 = express.Router();
4 
5v1.get('/users', async (req, res, next) => {
6 try {
7 const users = await req.db.users.findAll();
8 res.json(users.map(({ id, name }) => ({ id, name })));
9 } catch (err) {
10 next(err);
11 }
12});
13 
14v1.post('/users', async (req, res, next) => {
15 try {
16 const user = await req.db.users.create({ name: req.body.name });
17 res.status(201).json({ id: user.id, name: user.name });
18 } catch (err) {
19 next(err);
20 }
21});
22 
23const v2 = express.Router();
24 
25v2.get('/users', async (req, res, next) => {
26 try {
27 const page = Number(req.query.page) || 1;
28 const perPage = 25;
29 const { rows, count } = await req.db.users.findAndPaginate({ page, perPage });
30 res.json({
31 data: rows.map(({ id, name, email }) => ({ id, name, email })),
32 meta: { page, perPage, total: count },
33 });
34 } catch (err) {
35 next(err);
36 }
37});
38 
39v2.post('/users', validateUserPayload, async (req, res, next) => {
40 try {
41 const user = await req.db.users.create(req.body);
42 res.status(201).json({ id: user.id, name: user.name, email: user.email });
43 } catch (err) {
44 next(err);
45 }
46});
47 
48const api = express.Router();
49api.use('/v1', v1);
50api.use('/v2', v2);
51 
52module.exports = api;
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Separate Router instances let you evolve an API version without touching older ones.
  2. 2Forwarding caught errors to next(err) keeps async route handlers from crashing the process.
  3. 3Mounting routers under path prefixes turns version names into a single composition step.

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