In this post, we will learn how to route requests using Router on Express Server.

Preface

Routing determines how an application responds to a request for particular endpoint.

For an introduction to routing, please see Express docs

When a server manages multiple objects it results in serving multiple endpoints. At this point, it would become harder to main the application logic at one place. Express helps us divide the application logic based on objects it serves into individual routes.

We will demonstrate a simple example of routing on a node server

You can skip to tutorial and refer to this commit for source code

Requirements

• This post assumes users have the knowledge of basic express server. If you are not familiar with it please refer to demo example

• We will be using postman to test our end points

Basic Application

In this section we will create two routes user and item.
For each of these routes we will add GET, PUT and POST HTTP Requests.

Route for items

• Create a file items.ts
• Create router from Express

import express from "express";
export const router = express.Router();

• Add HTTP GET Request to read an item

// GET Method
router.get("/:id", (req, res) => {
  res.send(`You are requesting an item with id: ${req.params["id"]}`);
});

• Add HTTP POST Request to write an item

// POST Method
router.post("/", (req, res) => {
  res.send(`You are posting an item with params: ${req.params}`);
});

• Add HTTP PUT Request to update an item

// PUT Method
router.put("/:id", (req, res) => {
  res.send(`You are updating an item with id: ${req.params["id"]}`);
});

• Stitching all the above parts together we get our items.ts module

Using item Route in app

• Create index.ts if you have not already
• Import router from items.ts

import express from "express";
import { router as item_router } from "./items";

• Create an express app if you haven't already

const app = express();
const port = 3000;

• Route requests on items on app to item_router

app.use("/tdsvc/item", item_router);

• Listen to requests on the port (3000)

app.listen(port, (err?) => {
  if (err) {
    return console.error(err);
  }
  return console.log(`server is listening on port: ${port}`);
});

• Stitching all the parts together, we get our index.ts

Running the server

• If you are using node to run your server, use the flag --es-module-specifier-resolution=node
• This tells node to import modules without extensions .js or .mjs
• Update your start script in package.json

  "scripts": {
    "start": "tsc && node --es-module-specifier-resolution=node dist/index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
..

• Run your server by using the command npm start
• You should see a message similar to below on your terminal

$ npm start

> tdsvc@0.1.0 start D:\Workspace\blog-series\tdsvc
> tsc && node --es-module-specifier-resolution=node dist/index.js  

server is listening on port: 3000

Testing the requests on item

• Open postman app or browser plugin

• Send a GET request to read an item

  • Method: GET
  • URL: http://localhost:3000/tdsvc/item/1
  • You should see a response as shown below

• Send a POST request to write an item

  • Method: POST
  • URL: http://localhost:3000/tdsvc/item/
  • Request Body with json format

    {
      "text": "item 1"
    }
  

  • You should see a response as shown below

• Send a PUT request to update an item

  • Method: PUT
  • URL: http://localhost:3000/tdsvc/item/1
  • Request Body with json format

     {
       "text": "updated item"
     }
  

  • You should see a response as shown below

Route for users

Repeat the steps we did for items

• Create a file users.ts
• Create router from Express

import express from "express";
export const router = express.Router();

• Add HTTP GET Request to read an item

// GET Method
router.get("/:id", (req, res) => {
  res.send(`You are requesting an user with id: ${req.params["id"]}`);
});

• Add HTTP POST Request to write an item

// POST Method
router.post("/", (req, res) => {
  res.send(`You are posting an user with params: ${req.params}`);
});

• Add *HTTP PUT Request * to update an item

// PUT Method
router.put("/:id", (req, res) => {
  console.log(req);
  res.send(`You are updating an user with id: ${req.params["id"]}`);
});

• Stitching all the above parts together we get our users.ts module

Using user Route in app

• Import router from users.ts

import { router as user_router } from "./users";

• Route requests on users on app to user_router

app.use("/tdsvc/user", user_router);

• Stitching both routes parts together, we get our new index.ts

Testing the requests on users

• Run the server

• Send a GET request to read an user

  • Method: GET
  • URL: http://localhost:3000/tdsvc/user/1
  • You should see a response as shown below

• Send a POST request to write an user

  • Method: POST
  • URL: http://localhost:3000/tdsvc/user/
  • Request Body with json format

    {
      "text": "user 1"
    }
  

  • You should see a response as shown below

• Send a PUT request to update an item

  • Method: PUT
  • URL: http://localhost:3000/tdsvc/user/1
  • Request Body with json format

     {
       "text": "updated user"
     }
  

  • You should see a response as shown below

Parsing Requests Payload

• Add express.json to parse JSON payloads in request body

app.use(express.json());

• Add express.urlencoded to parses requests with urlencoded payloads

app.use(express.urlencoded({ extended: true }));

Please check the full code in this commit

❤️ Congratulations 👏, you have successfully routed requests on a node server using Express and TypeScript

Thanks for reading through the entire article. Please reach out with questions, comments and/or feedback.