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

Space play ←→ step click any line
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.

Related explainers

javascript 
function evaluate(expression) {
  const tokens = tokenize(expression);
  let pos = 0;
 

Building a recursive descent calculator

parsing recursion operator-precedence
Intermediate 8 steps
javascript 
import { useState, useEffect, useCallback, useRef } from 'react';
 
const cache = new Map();
const inflight = new Map();

Building a stale-while-revalidate hook in React

caching request-deduplication custom-hooks
Advanced 10 steps
javascript 
import { useEffect, useRef, useState } from 'react';
 
export function useDelayedFlag(active, delay = 300) {
  const [visible, setVisible] = useState(false);

Delaying a loading spinner with a React hook

custom-hooks debouncing cleanup
Intermediate 8 steps
javascript 
const SWIPE_THRESHOLD = 80;
const MAX_TRANSLATE = 120;
 
export function attachSwipeToDismiss(element, onDismiss) {

Building a swipe-to-dismiss gesture in JS

touch-events gesture-detection dom-manipulation
Intermediate 10 steps
python 
from django.db import connections
from django.db.utils import OperationalError
from django.core.cache import caches
from django.http import JsonResponse

Building a health check endpoint in Django

health check monitoring database
Intermediate 7 steps
javascript 
const { pool } = require('./db');
 
function withTransaction() {
  return async (req, res, next) => {

A per-request transaction middleware in Express

middleware database-transactions connection-pooling
Advanced 7 steps

Share this explainer

Here's the card — post it anywhere.

Versioning an API with Express Routers — share card
Made with highlit — turn any snippet into a walkthrough like this in about a minute.
Explain your code