Node.js
Summary - Routing
Combine param, query and Router to write a user API.
Summary: User API
In this lesson we combine what we learned into a user API: route parameters, query parameters and express.Router together.
The API works like this: GET /users lists all users, GET /users/:id returns a single user, GET /search?q=... searches by name. The router groups user routes under /users; the search route stays at the app root. This is the skeleton of a real REST API: resource routes are grouped with a router, search is done with optional query parameters. We send JSON responses with res.json.
Combining the pieces
The API has three parts. First the router: userRouter.get("/", ...) and userRouter.get("/:id", ...), mounted with app.use("/users", userRouter). Second the search: app.get("/search", (req, res) => { ... req.query.q ... }).
In the :id route we find the user whose id matches with users.find. We convert the string parameter to a number with Number(req.params.id) because id in the users array is a number. In the /search route we take the search string with req.query.q and find users whose name contains it with users.filter. Each route returns JSON with res.json. This is the standard structure of REST APIs.
Exercise Write the user API
Define const userRouter = express.Router(). Define let users = [{ id: 1, name: "Ayşe" }, { id: 2, name: "Mehmet" }]. Add userRouter.get("/", (req, res) => res.json(users)). Add userRouter.get("/:id", (req, res) => { const user = users.find(function(u) { return u.id === Number(req.params.id); }); res.json(user); }). Mount with app.use("/users", userRouter). Add app.get("/search", (req, res) => { const found = users.filter(function(u) { return u.name.includes(req.query.q); }); res.json(found); }). The server requests /users/1.
Show example solution
const express = require("express");
const app = express();
const userRouter = express.Router();
let users = [{ id: 1, name: "Ayşe" }, { id: 2, name: "Mehmet" }];
userRouter.get("/", (req, res) => res.json(users));
userRouter.get("/:id", (req, res) => {
const user = users.find(function(u) { return u.id === Number(req.params.id); });
res.json(user);
});
app.use("/users", userRouter);
app.get("/search", (req, res) => {
const found = users.filter(function(u) { return u.name.includes(req.query.q); });
res.json(found);
});
const server = app.listen(3000, () => {
const http = require("http");
http.get("http://localhost:3000/users/1", (res) => {
let body = "";
res.on("data", (c) => body += c);
res.on("end", () => { console.log("Reply: " + body); server.close(); });
});
});
Test yourself
-
Which route returns a single user?
GET /users/5
- GET /users/:id
- GET /users
- GET /search?q=5
- POST /users
Show answer
GET /users/:id — /users/:id returns one user via a route parameter.
-
Match each piece to its role
- userRouter.get('/:id')
- Single user
- req.params.id
- Route id
- req.query.q
- Search string
- app.use('/users', ...)
- Mounts the router
Next lesson: Quiz model
