Use TypeScript to Build a Node API with Express

Like it or not, JavaScript has been helping developers power the Internet since 1995. In that time, JavaScript usage has grown from small user experience enhancements to complex full-stack applications using Node.js on the server and one of many frameworks on the client such as Angular, React, or Vue.

Today, building JavaScript applications at scale remains a challenge. More and more teams are turning to TypeScript to supplement their JavaScript projects.

Node.js server applications can benefit from using TypeScript, as well. The goal of this tutorial is to show you how to build a new Node.js application using TypeScript and Express.

The Case for TypeScript

As a web developer, I long ago stopped resisting JavaScript, and have grown to appreciate its flexibility and ubiquity. Language features added to ES2015 and beyond have significantly improved its utility and reduced common frustrations of writing applications.

However, larger JavaScript projects demand tools such as ESLint to catch common mistakes, and greater discipline to saturate the code base with useful tests. As with any software project, a healthy team culture that includes a peer review process can improve quality and guard against issues that can creep into a project.

The primary benefits of using TypeScript are to catch more errors before they go into production and make it easier to work with your code base.

TypeScript is not a different language. It’s a flexible superset of JavaScript with ways to describe optional data types. All “standard” and valid JavaScript is also valid TypeScript. You can dial in as much or little as you desire.

As soon as you add the TypeScript compiler or a TypeScript plugin to your favorite code editor, there are immediate safety and productivity benefits. TypeScript can alert you to misspelled functions and properties, detect passing the wrong types of arguments or the wrong number of arguments to functions, and provide smarter autocomplete suggestions.

Build a Guitar Inventory Application with TypeScript and Node.js

Among guitar players, there’s a joke everyone should understand.

Q: “How many guitars do you need?”

A: “n + 1. Always one more.”

In this tutorial, you are going to create a new Node.js application to keep track of an inventory of guitars. In a nutshell, this tutorial uses Node.js with Express, EJS, and PostgreSQL on the backend, Vue, Materialize, and Axios on the frontend, Okta for account registration and authorization, and TypeScript to govern the JavaScripts!

Create Your Node.js Project

Open up a terminal (Mac/Linux) or a command prompt (Windows) and type the following command:

node --version

If you get an error, or the version of Node.js you have is less than version 14, you’ll need to install Node.js. On Mac or Linux, I recommend you first install nvm and use nvm to install Node.js. On Windows, I recommend you use Chocolatey.

After ensuring you have a recent version of Node.js installed, create a folder for your project.

mkdir guitar-inventory
cd guitar-inventory

Use npm to initialize a package.json file.

npm init -y

Hello, world!

In this sample application, Express is used to serve web pages and implement an API. Dependencies are installed using npm. Add Express to your project with the following command.

npm install express@4

Next, open the project in your editor of choice.

If you don’t already have a favorite code editor, I use and recommend Visual Studio Code. VS Code has exceptional support for JavaScript and Node.js, such as smart code completion and debugging, and there’s a vast library of free extensions contributed by the community.

Create a folder named src. In this folder, create a file named index.js. Open the file and add the following JavaScript.

const express = require( "express" );
const app = express();
const port = 8080; // default port to listen

// define a route handler for the default home page
app.get( "/", ( req, res ) => {
    res.send( "Hello world!" );
} );

// start the Express server
app.listen( port, () => {
    console.log( `server started at http://localhost:${ port }` );
} );

Next, update package.json to instruct npm on how to run your application. Change the main property value to point to src/index.js, and add a start script to the scripts object.

  "main": "src/index.js",
  "scripts": {
    "start": "node .",
    "test": "echo \"Error: no test specified\" && exit 1"
  },

Now, from the terminal or command line, you can launch the application.

npm run start

If all goes well, you should see this message written to the console.

server started at http://localhost:8080

Launch your browser and navigate to http://localhost:8080. You should see the text “Hello world!”

Note: To stop the web application, you can go back to the terminal or command prompt and press CTRL+C.

Set Up Your Node.js Project to Use TypeScript

The first step is to add the TypeScript compiler. You can install the compiler as a developer dependency using the --save-dev flag.

npm install --save-dev typescript@4

The next step is to add a tsconfig.json file. This file instructs TypeScript how to compile (transpile) your TypeScript code into plain JavaScript.

Create a file named tsconfig.json in the root folder of your project, and add the following configuration.

{
    "compilerOptions": {
        "module": "commonjs",
        "esModuleInterop": true,
        "target": "es6",
        "noImplicitAny": true,
        "moduleResolution": "node",
        "sourceMap": true,
        "outDir": "dist",
        "baseUrl": ".",
        "paths": {
            "*": [
                "node_modules/*"
            ]
        }
    },
    "include": [
        "src/**/*"
    ]
}

Based on this tsconfig.json file, the TypeScript compiler will (attempt to) compile any files ending with .ts it finds in the src folder, and store the results in a folder named dist. Node.js uses the CommonJS module system, so the value for the module setting is commonjs. Also, the target version of JavaScript is ES6 (ES2015), which is compatible with modern versions of Node.js.

It’s also a great idea to add tslint and create a tslint.json file that instructs TypeScript how to lint your code. If you’re not familiar with linting, it is a code analysis tool to alert you to potential problems in your code beyond syntax issues.

Install tslint as a developer dependency.

npm install --save-dev tslint

Next, create a new file in the root folder named tslint.json file and add the following configuration.

{
    "defaultSeverity": "error",
    "extends": [
        "tslint:recommended"
    ],
    "jsRules": {},
    "rules": {
        "trailing-comma": [ false ]
    },
    "rulesDirectory": []
}

Next, update your package.json to change main to point to the new dist folder created by the TypeScript compiler. Also, add a couple of scripts to execute TSLint and the TypeScript compiler just before starting the Node.js server.

  "main": "dist/index.js",
  "scripts": {
    "prebuild": "tslint -c tslint.json -p tsconfig.json --fix",
    "build": "tsc",
    "prestart": "npm run build",
    "start": "node .",
    "test": "echo \"Error: no test specified\" && exit 1"
  },

Finally, change the extension of the src/index.js file from .js to .ts, the TypeScript extension, and run the start script.

npm run start

Note: You can run TSLint and the TypeScript compiler without starting the Node.js server using npm run build.

TypeScript errors

Oh no! Right away, you may see some errors logged to the console like these.

ERROR: /Users/reverentgeek/Projects/guitar-inventory/src/index.ts[12, 5]: Calls to 'console.log' are not allowed.

src/index.ts:1:17 - error TS2580: Cannot find name 'require'. Do you need to install type definitions for node? Try `npm i @types/node`.

1 const express = require( "express" );
                  ~~~~~~~

src/index.ts:6:17 - error TS7006: Parameter 'req' implicitly has an 'any' type.

6 app.get( "/", ( req, res ) => {
                  ~~~

The two most common errors you may see are syntax errors and missing type information. TSLint considers using console.log to be an issue for production code. The best solution is to replace uses of console.log with a logging framework such as winston. For now, add the following comment to src/index.ts to disable the rule.

app.listen( port, () => {
    // tslint:disable-next-line:no-console
    console.log( `server started at http://localhost:${ port }` );
} );

TypeScript prefers to use the import module syntax over require, so you’ll start by changing the first line in src/index.ts from:

const express = require( "express" );

to:

import express from "express";

Getting the right types

To assist TypeScript developers, library authors and community contributors publish companion libraries called TypeScript declaration files. Declaration files are published to the DefinitelyTyped open source repository, or sometimes found in the original JavaScript library itself.

Update your project so that TypeScript can use the type declarations for Node.js and Express.

npm install --save-dev @types/node@16 @types/express@4

Next, rerun the start script and verify there are no more errors.

npm run start

Build a Better User Interface with Materialize and EJS

Your Node.js application is off to a great start, but perhaps not the best looking, yet. This step adds Materialize, a modern CSS framework based on Google’s Material Design, and Embedded JavaScript Templates (EJS), an HTML template language for Express. Materialize and EJS are a good foundation for a much better UI.

First, install EJS as a dependency.

npm install ejs@3

Next, make a new folder under /src named views. In the /src/views folder, create a file named index.ejs. Add the following code to /src/views/index.ejs.

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Guitar Inventory</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0/css/materialize.min.css">
    <link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">
</head>
<body>
    <div class="container">
        <h1 class="header">Guitar Inventory</h1>
        <a class="btn" href="/guitars"><i class="material-icons right">arrow_forward</i>Get started!</a>
    </div>
</body>
</html>

Update /src/index.ts with the following code.

import express from "express";
import path from "path";
const app = express();
const port = 8080; // default port to listen

// Configure Express to use EJS
app.set( "views", path.join( __dirname, "views" ) );
app.set( "view engine", "ejs" );

// define a route handler for the default home page
app.get( "/", ( req, res ) => {
    // render the index template
    res.render( "index" );
} );

// start the express server
app.listen( port, () => {
    // tslint:disable-next-line:no-console
    console.log( `server started at http://localhost:${ port }` );
} );

Add an asset build script for Typescript

The TypeScript compiler does the work of generating the JavaScript files and copies them to the dist folder. However, it does not copy the other types of files the project needs to run, such as the EJS view templates. To accomplish this, create a build script that copies all the other files to the dist folder.

Install the needed modules and TypeScript declarations using these commands.

npm install --save-dev ts-node@10 shelljs@0.8 fs-extra@10 nodemon@2 rimraf@3 npm-run-all@4
npm install --save-dev @types/fs-extra@9 @types/shelljs@0.8

Here is a quick overview of the modules you just installed.

Make a new folder in the root of the project named tools. Create a file in the tools folder named copyAssets.ts. Copy the following code into this file.

import * as shell from "shelljs";

// Copy all the view templates
shell.cp( "-R", "src/views", "dist/" );

Update npm scripts

Update the scripts in package.json to the following code.

  "scripts": {
    "clean": "rimraf dist/*",
    "copy-assets": "ts-node tools/copyAssets",
    "lint": "tslint -c tslint.json -p tsconfig.json --fix",
    "tsc": "tsc",
    "build": "npm-run-all clean lint tsc copy-assets",
    "dev:start": "npm-run-all build start",
    "dev": "nodemon --watch src -e ts,ejs --exec npm run dev:start",
    "start": "node .",
    "test": "echo \"Error: no test specified\" && exit 1"
  },

Note: If you are not familiar with using npm scripts, they can be very powerful and useful to any Node.js project. Scripts can be chained together in several ways. One way to chain scripts together is to use the pre and post prefixes. For example, if you have one script labeled start and another labeled prestart, executing npm run start at the terminal will first run prestart, and only after it successfully finishes does start run.

Now run the application and navigate to http://localhost:8080.

npm run dev

The home page is starting to look better! Of course, the Get Started button leads to a disappointing error message. No worries! The fix for that is coming soon!

A Better Way to Manage Configuration Settings in Node.js

Node.js applications typically use environment variables for configuration. However, managing environment variables can be a chore. A popular module for managing application configuration data is dotenv.

Install dotenv as a project dependency.

npm install dotenv@10
npm install --save-dev @types/dotenv@8

Create a file named .env in the root folder of the project, and add the following code.

# Set to production when deploying to production
NODE_ENV=development

# Node.js server configuration
SERVER_PORT=8080

Note: When using a source control system such as git, do not add the .env file to source control. Each environment requires a custom .env file. It is recommended you document the values expected in the .env file in the project README or a separate .env.sample file.

Now, update src/index.ts to use dotenv to configure the application server port value.

import dotenv from "dotenv";
import express from "express";
import path from "path";

// initialize configuration
dotenv.config();

// port is now available to the Node.js runtime 
// as if it were an environment variable
const port = process.env.SERVER_PORT;

const app = express();

// Configure Express to use EJS
app.set( "views", path.join( __dirname, "views" ) );
app.set( "view engine", "ejs" );

// define a route handler for the default home page
app.get( "/", ( req, res ) => {
    // render the index template
    res.render( "index" );
} );

// start the express server
app.listen( port, () => {
    // tslint:disable-next-line:no-console
    console.log( `server started at http://localhost:${ port }` );
} );

You will use the .env for much more configuration information as the project grows.

Easily Add Authentication to Node and Express

Adding user registration and login (authentication) to any application is not a trivial task. The good news is Okta makes this step very easy.

Before you begin, you’ll need a free Okta developer account. Install the Okta CLI and run okta register to sign up for a new account. If you already have an account, run okta login. Then, run okta apps create. Select the default app name, or change it as you see fit. Choose Web and press Enter.

Select Other. Then, change the Redirect URI to http://localhost:8080/authorization-code/callback and accept the default Logout Redirect URI of http://localhost:8080.

Okta application configuration has been written to: /path/to/app/.okta.env

export OKTA_OAUTH2_ISSUER="https://dev-133337.okta.com/oauth2/default"
export OKTA_OAUTH2_CLIENT_ID="0oab8eb55Kb9jdMIr5d6"
export OKTA_OAUTH2_CLIENT_SECRET="NEVER-SHOW-SECRETS"

Copy and paste the following code into your .env file.

# Okta configuration
OKTA_ORG_URL=https://{yourOktaDomain}
OKTA_CLIENT_ID={yourClientId}
OKTA_CLIENT_SECRET={yourClientSecret}

Enable self-service registration

One of the great features of Okta is allowing users of your application to sign up for an account. By default, this feature is disabled, but you can easily enable it. Run okta login to get the URL for your Okta org. Open the result in your favorite browser and log in to the Okta Admin Console.

1. Click on the Directory menu and select Self-Service Registration
2. Click on the Enable Registration button.
3. If you don’t see this button, click Edit and change Self-service registration to Enabled.
4. Click the Save button at the bottom of the form.

Secure your Node.js application

The last step to securing your Node.js application is to configure Express to use the Okta OpenId Connect (OIDC) middleware.

npm install @okta/oidc-middleware@4 express-session@1
npm install --save-dev @types/express-session@1

Next, update your .env file to add a HOST_URL and SESSION_SECRET value. You may change the SESSION_SECRET value to any string you wish.

# Node.js server configuration
SERVER_PORT=8080
HOST_URL=http://localhost:8080
SESSION_SECRET=MySuperCoolAndAwesomeSecretForSigningSessionCookies

Create a folder under src named middleware. Add a file to the src/middleware folder named sessionAuth.ts. Add the following code to src/middleware/sessionAuth.ts.

import { ExpressOIDC } from "@okta/oidc-middleware";
import session from "express-session";

export const register = ( app: any ) => {
    // Create the OIDC client
    const oidc = new ExpressOIDC( {
        client_id: process.env.OKTA_CLIENT_ID,
        client_secret: process.env.OKTA_CLIENT_SECRET,
        issuer: `${ process.env.OKTA_ORG_URL }/oauth2/default`,
        redirect_uri: `${ process.env.HOST_URL }/authorization-code/callback`,
        appBaseUrl:`${ process.env.HOST_URL }`,
        scope: "openid profile"
    } );

    // Configure Express to use authentication sessions
    app.use( session( {
        resave: true,
        saveUninitialized: false,
        secret: process.env.SESSION_SECRET
    } ) );

    // Configure Express to use the OIDC client router
    app.use( oidc.router );

    // add the OIDC client to the app.locals
    app.locals.oidc = oidc;
};

At this point, if you are using a code editor like VS Code, you may see TypeScript complaining about the @okta/oidc-middleware module. At the time of this writing, this module does not yet have an official TypeScript declaration file. For now, create a file in the src folder named global.d.ts and add the following code.

declare module "@okta/oidc-middleware";

Refactor routes

As the application grows, you will add many more routes. It is a good idea to define all the routes in one area of the project. Make a new folder under src named routes. Add a new file to src/routes named index.ts. Then, add the following code to this new file.

import * as express from "express";

export const register = ( app: express.Application ) => {
    const oidc = app.locals.oidc;

    // define a route handler for the default home page
    app.get( "/", ( req: any, res ) => {
        res.render( "index" );
    } );

    // define a secure route handler for the login page that redirects to /guitars
    app.get( "/login", oidc.ensureAuthenticated(), ( req, res ) => {
        res.redirect( "/guitars" );
    } );

    // define a route to handle logout
    app.get( "/logout", ( req: any, res ) => {
        req.logout();
        res.redirect( "/" );
    } );

    // define a secure route handler for the guitars page
    app.get( "/guitars", oidc.ensureAuthenticated(), ( req: any, res ) => {
        res.render( "guitars" );
    } );
};

Next, update src/index.ts to use the sessionAuth and routes modules you created.

import dotenv from "dotenv";
import express from "express";
import path from "path";
import * as sessionAuth from "./middleware/sessionAuth";
import * as routes from "./routes";

// initialize configuration
dotenv.config();

// port is now available to the Node.js runtime
// as if it were an environment variable
const port = process.env.SERVER_PORT;

const app = express();

// Configure Express to use EJS
app.set( "views", path.join( __dirname, "views" ) );
app.set( "view engine", "ejs" );

// Configure session auth
sessionAuth.register( app );

// Configure routes
routes.register( app );

// start the express server
app.listen( port, () => {
    // tslint:disable-next-line:no-console
    console.log( `server started at http://localhost:${ port }` );
} );

Next, create a new file for the guitar list view template at src/views/guitars.ejs and enter the following HTML.

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Guitar Inventory</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0/css/materialize.min.css">
    <link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">
</head>
<body>
    <div class="container">
        <h1 class="header">Guitar Inventory</h1>
        <p>Your future list of guitars!</p>
    </div>
</body>
</html>

Finally, run the application.

npm run dev

Note: To verify authentication is working as expected, open a new browser or use a private/incognito browser window.

Click the Get Started button. If everything goes well, log in with your Okta account, and Okta should automatically redirect you back to the “Guitar List” page!

Add a Navigation Menu to Your Node + Typescript App

With authentication working, you can take advantage of the user profile information returned from Okta. The OIDC middleware automatically attaches a userContext object and an isAuthenticated() function to every request. This userContext has a userinfo property that contains information that looks like the following object.

{ 
  sub: '00abc12defg3hij4k5l6',
  name: 'First Last',
  locale: 'en-US',
  preferred_username: 'account@company.com',
  given_name: 'First',
  family_name: 'Last',
  zoneinfo: 'America/Los_Angeles',
  updated_at: 1539283620 
}

The first step is get the user profile object and pass it to the views as data. Update the src/routes/index.ts with the following code.

import * as express from "express";

export const register = ( app: express.Application ) => {
    const oidc = app.locals.oidc;

    // define a route handler for the default home page
    app.get( "/", ( req: any, res ) => {
        const user = req.userContext ? req.userContext.userinfo : null;
        res.render( "index", { isAuthenticated: req.isAuthenticated(), user } );
    } );

    // define a secure route handler for the login page that redirects to /guitars
    app.get( "/login", oidc.ensureAuthenticated(), ( req, res ) => {
        res.redirect( "/guitars" );
    } );

    // define a route to handle logout
    app.get( "/logout", ( req: any, res ) => {
        req.logout();
        res.redirect( "/" );
    } );

    // define a secure route handler for the guitars page
    app.get( "/guitars", oidc.ensureAuthenticated(), ( req: any, res ) => {
        const user = req.userContext ? req.userContext.userinfo : null;
        res.render( "guitars", { isAuthenticated: req.isAuthenticated(), user } );
    } );
};

Make a new folder under src/views named partials. Create a new file in this folder named nav.ejs. Add the following code to src/views/partials/nav.ejs.

<nav>
    <div class="nav-wrapper">
        <a href="/" class="brand-logo"><% if ( user ) { %><%= user.name %>'s <% } %>Guitar Inventory</a>
        <ul id="nav-mobile" class="right hide-on-med-and-down">
            <li><a href="/guitars">My Guitars</a></li>
            <% if ( isAuthenticated ) { %>
            <li><a href="/logout">Logout</a></li>
            <% } %>
            <% if ( !isAuthenticated ) { %>
            <li><a href="/login">Login</a></li>
            <% } %>
        </ul>
    </div>
</nav>

Modify the src/views/index.ejs and src/views/guitars.ejs files. Immediately following the <body> tag, insert the following code.

<body>
    <%- include('partials/nav.ejs') %>

With these changes in place, your application now has a navigation menu at the top that changes based on the login status of the user.

Create an API with Node and PostgreSQL

The next step is to add the API to the Guitar Inventory application. However, before moving on, you need a way to store data.

Create a PostgreSQL database

This tutorial uses PostgreSQL. To make things easier, use Docker to set up an instance of PostgreSQL. If you don’t already have Docker installed, you can follow the install guide.

Once you have Docker installed, run the following command to download the latest PostgreSQL container.

docker pull postgres:latest

Now, run this command to create an instance of a PostgreSQL database server. Feel free to change the administrator password value.

docker run -d --name guitar-db -p 5432:5432 -e 'POSTGRES_PASSWORD=p@ssw0rd42' postgres

Note: If you already have PostgreSQL installed locally, you will need to change the -p parameter to map port 5432 to a different port that does not conflict with your existing instance of PostgreSQL.

Here is a quick explanation of the previous Docker parameters.

Note: If you restart your computer, may need to restart the Docker container. You can do that using the docker start guitar-db command.

Install the PostgreSQL client module and type declarations using the following commands.

npm install pg@8 pg-promise@10
npm install --save-dev @types/pg@8

Database configuration settings

Add the following settings to the end of the .env file.

# Postgres configuration
PGHOST=localhost
PGUSER=postgres
PGDATABASE=postgres
PGPASSWORD=p@ssw0rd42
PGPORT=5432

Note: If you changed the database administrator password, be sure to replace the default p@ssw0rd42 with that password in this file.

Add a database build script

You need a build script to initialize the PostgreSQL database. This script should read in a .pgsql file and execute the SQL commands against the local database.

In the tools folder, create two files: initdb.ts and initdb.pgsql. Copy and paste the following code into initdb.ts.

import dotenv from "dotenv";
import fs from "fs-extra";
import { Client } from "pg";

const init = async () => {
    // read environment variables
    dotenv.config();
    // create an instance of the PostgreSQL client
    const client = new Client();
    try {
        // connect to the local database server
        await client.connect();
        // read the contents of the initdb.pgsql file
        const sql = await fs.readFile( "./tools/initdb.pgsql", { encoding: "UTF-8" } );
        // split the file into separate statements
        const statements = sql.split( /;\s*$/m );
        for ( const statement of statements ) {
            if ( statement.length > 3 ) {
                // execute each of the statements
                await client.query( statement );
            }
        }
    } catch ( err ) {
        console.log( err );
        throw err;
    } finally {
        // close the database client
        await client.end();
    }
};

init().then( () => {
    console.log( "finished" );
} ).catch( () => {
    console.log( "finished with errors" );
} );

Next, copy and paste the following code into initdb.pgsql.

-- Drops guitars table
DROP TABLE IF EXISTS guitars;

-- Creates guitars table
CREATE TABLE IF NOT EXISTS guitars (
    id INT NOT NULL PRIMARY KEY GENERATED ALWAYS AS IDENTITY
    , user_id varchar(50) NOT NULL
    , brand varchar(50) NOT NULL
    , model varchar(50) NOT NULL
    , year smallint NULL 
    , color varchar(50) NULL
);

Next, add a new script to package.json.

    "initdb": "ts-node tools/initdb",

Now, go to the terminal and run the new script.

npm run initdb

You should see the message finished at the console. A new table named guitars is now in your database! Any time you want to reset your database, just rerun the script.

Add API routes in Node.js

To complete the API, you need to add new routes to Express to create, query, update, and delete guitars. First, create a new file under src/routes named api.ts. Add the following code to this file.

import * as express from "express";
import pgPromise, { ParameterizedQuery } from "pg-promise";

export const register = ( app: express.Application ) => {
    const oidc = app.locals.oidc;
    const port = parseInt( process.env.PGPORT || "5432", 10 );
    const config = {
        database: process.env.PGDATABASE || "postgres",
        host: process.env.PGHOST || "localhost",
        port,
        user: process.env.PGUSER || "postgres"
    };

    const pgp = pgPromise();
    const db = pgp( config );

    app.get( `/api/guitars/all`, oidc.ensureAuthenticated(), async ( req: any, res ) => {
        try {
            const userId = req.userContext.userinfo.sub;
            const guitars = await db.any( `
                SELECT
                    id
                    , brand
                    , model
                    , year
                    , color
                FROM    guitars
                WHERE   user_id = $1
                ORDER BY year, brand, model`, [ userId ] );
            return res.json( guitars );
        } catch ( err ) {
            // tslint:disable-next-line:no-console
            console.error(err);
            res.json( { error: err.message || err } );
        }
    } );

    app.post( `/api/guitars/add`, oidc.ensureAuthenticated(), async ( req: any, res ) => {
        try {
            const userId = req.userContext.userinfo.sub;
            const { brand, model, year, color } = req.body;
            const addGuitar = new ParameterizedQuery( { text: `
                INSERT INTO guitars(user_id, brand, model, year, color)
                VALUES($1, $2, $3, $4, $5)
                RETURNING id;
            `,
            values: [ userId, brand, model, year, color ]
            } );
            const id = await db.one( addGuitar );
            return res.json( { id } );
        } catch ( err ) {
            // tslint:disable-next-line:no-console
            console.error(err);
            res.json( { error: err.message || err } );
        }
    } );

    app.delete( `/api/guitars/remove/:id`, oidc.ensureAuthenticated(), async ( req: any, res ) => {
        try {
            const userId = req.userContext.userinfo.sub;
            const id = await db.result( `
                DELETE
                FROM    guitars
                WHERE   user_id = $1
                AND     id = $2`,
                [ userId, req.params.id ], 
                ( r: any ) => r.rowCount );
            return res.json( { id } );
        } catch ( err ) {
            // tslint:disable-next-line:no-console
            console.error(err);
            res.json( { error: err.message || err } );
        }
    } );
};

Update src/routes/index.ts to include the new api module.

import * as express from "express";
import * as api from "./api";

export const register = ( app: express.Application ) => {
    const oidc = app.locals.oidc;

    // define a route handler for the default home page
    app.get( "/", ( req: any, res ) => {
        const user = req.userContext ? req.userContext.userinfo : null;
        res.render( "index", { isAuthenticated: req.isAuthenticated(), user } );
    } );

    // define a secure route handler for the login page that redirects to /guitars
    app.get( "/login", oidc.ensureAuthenticated(), ( req, res ) => {
        res.redirect( "/guitars" );
    } );

    // define a route to handle logout
    app.get( "/logout", ( req: any, res ) => {
        req.logout();
        res.redirect( "/" );
    } );

    // define a secure route handler for the guitars page
    app.get( "/guitars", oidc.ensureAuthenticated(), ( req: any, res ) => {
        const user = req.userContext ? req.userContext.userinfo : null;
        res.render( "guitars", { isAuthenticated: req.isAuthenticated(), user } );
    } );

    api.register( app );
};

Finally, update src/index.ts to add a new configuration option immediately following the line to create the Express application. This code enables Express to parse incoming JSON data.

const app = express();

// Configure Express to parse incoming JSON data
app.use( express.json() );

Update the User Interface with Vue, Axios, and Parcel

The API is ready. To complete the application, you need to add some code to the frontend to consume the API. You can take advantage of TypeScript with frontend code, as well.

This final step of the project uses Vue for frontend rendering, Axios for making HTTP calls to the backend API, and Parcel to both transpile TypeScript and bundle all the dependencies together into a single JavaScript file.

First, install new dependencies at the console using the following commands.

npm install axios@0.24 vue@2 materialize-css@1
npm install --save-dev parcel-bundler @types/axios@0.14 @types/materialize-css@1 @types/vue@2

Make a new folder under src named public. Make a new folder under src/public named js. Create a file under src/public/js named main.ts and add the following code.

import axios from "axios";
import * as M from "materialize-css";
import Vue from "vue";

// tslint:disable-next-line no-unused-expression
new Vue( {
    computed: {
        hazGuitars(): boolean {
            return this.isLoading === false && this.guitars.length > 0;
        },
        noGuitars(): boolean {
            return this.isLoading === false && this.guitars.length === 0;
        }
    },
    data: {
        brand: "",
        color: "",
        guitars: [],
        isLoading: true,
        model: "",
        selectedGuitar: "",
        selectedGuitarId: 0,
        year: ""
    },
    el: "#app",
    methods: {
        addGuitar: function {
            const guitar = {
                brand: this.brand,
                color: this.color,
                model: this.model,
                year: this.year
            };
            axios
                .post( "/api/guitars/add", guitar )
                .then( () => {
                    this.$refs.year.focus();
                    this.brand = "";
                    this.color = "";
                    this.model = "";
                    this.year = "";
                    this.loadGuitars();
                } )
                .catch( ( err: any ) => {
                    // tslint:disable-next-line:no-console
                    console.log( err );
                } );
        },
        confirmDeleteGuitar: function ( id: string ) {
            const guitar = this.guitars.find( ( g ) => g.id === id );
            this.selectedGuitar = `${ guitar.year } ${ guitar.brand } ${ guitar.model }`;
            this.selectedGuitarId = guitar.id;
            const dc = this.$refs.deleteConfirm;
            const modal = M.Modal.init( dc );
            modal.open();
        },
        deleteGuitar: function( id: string ) {
            axios
                .delete( `/api/guitars/remove/${ id }` )
                .then( this.loadGuitars )
                .catch( ( err: any ) => {
                    // tslint:disable-next-line:no-console
                    console.log( err );
                } );
        },
        loadGuitars: function() {
            axios
                .get( "/api/guitars/all" )
                .then( ( res: any ) => {
                    this.isLoading = false;
                    this.guitars = res.data;
                } )
                .catch( ( err: any ) => {
                    // tslint:disable-next-line:no-console
                    console.log( err );
                } );
        }
    },
    mounted: function() {
        return this.loadGuitars();
    }
} );

Update tsconfig.json to exclude the src/public folder from the backend Node.js build process.

{
    "compilerOptions": {
        "module": "commonjs",
        "esModuleInterop": true,
        "target": "es6",
        "noImplicitAny": true,
        "moduleResolution": "node",
        "sourceMap": true,
        "outDir": "dist",
        "baseUrl": ".",
        "paths": {
            "*": [
                "node_modules/*"
            ]
        }
    },
    "include": [
        "src/**/*"
    ],
    "exclude": [
        "src/public"
    ]
}

Create a new tsconfig.json file under src/public/js and add the following code. This TypeScript configuration is to compile main.ts for use in the browser.

{
    "compilerOptions": {
        "lib": [
            "es6",
            "dom"
        ],
        "noImplicitAny": true,
        "allowJs": true,
        "target": "es5",
        "strict": true,
        "module": "es6",
        "moduleResolution": "node",
        "outDir": "../../../dist/public/js",
        "sourceMap": true
    }
}

Next, update src/index.ts to configure Express to serve static files from the public folder. Add this line after the code that configures Express to use EJS.

...
// Configure Express to use EJS
app.set( "views", path.join( __dirname, "views" ) );
app.set( "view engine", "ejs" );

// Configure Express to serve static files in the public folder
app.use( express.static( path.join( __dirname, "public" ) ) );

Update src/views/guitars.ejs to add the Vue application template and a reference to the js/main.js file.

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Guitar Inventory</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/materialize/1.0.0/css/materialize.min.css">
    <link rel="stylesheet" href="https://fonts.googleapis.com/icon?family=Material+Icons">
</head>
<body>
    <%- include('partials/nav.ejs') %>
    <div class="container">
        <div id="app">
            <div class="row" id="guitarList">
                <h3>Guitar list</h3>
                <table v-if="hazGuitars">
                    <thead>
                        <tr>
                            <th>Year</th>
                            <th>Brand</th>
                            <th>Model</th>
                            <th>Color</th>
                            <th></th>
                        </tr>
                    </thead>
                    <tbody>
                        <tr v-for="guitar in guitars">
                            <td>{{ guitar.year }}</td>
                            <td>{{ guitar.brand }}</td>
                            <td>{{ guitar.model }}</td>
                            <td>{{ guitar.color }}</td>
                            <td>
                                <button id="guitarDelete" @click="confirmDeleteGuitar(guitar.id)" class="btn-small"><i class="material-icons right">delete</i>Delete</button>
                            </td>
                        </tr>
                    </tbody>
                </table>
                <p v-if="noGuitars">No guitars yet!</p>
            </div>
            <div class="row" id="guitarEdit">
                <h3>Add a guitar</h3>
                <form class="col s12" @submit.prevent="addGuitar">
                    <div class="row">
                        <div class="input-field col s6">
                            <input v-model="year" ref="year" placeholder="2005" id="year" type="text" class="validate">
                            <label for="brand">Year</label>
                        </div>
                        <div class="input-field col s6">
                            <input v-model="brand" ref="brand" placeholder="Paul Reed Smith" id="brand" type="text" class="validate">
                            <label for="brand">Brand</label>
                        </div>
                    </div>
                    <div class="row">
                        <div class="input-field col s6">
                            <input v-model="model" ref="model" placeholder="Custom 24" id="model" type="text" class="validate">
                            <label for="model">Model</label>
                        </div>
                        <div class="input-field col s6">
                            <input v-model="color" ref="color" placeholder="Whale Blue" id="color" type="text" class="validate">
                            <label for="model">Color</label>
                        </div>
                    </div>
                    <button id="guitarEditSubmit" class="btn" type="submit"><i class="material-icons right">send</i>Submit</button>
                </form>
            </div>
            <div id="deleteConfirm" ref="deleteConfirm" class="modal">
                <div class="modal-content">
                    <h4>Confirm delete</h4>
                    <p>Delete {{ selectedGuitar }}?</p>
                </div>
                <div class="modal-footer">
                    <button @click="deleteGuitar(selectedGuitarId)" class="modal-close btn-flat">Ok</button>
                    <button class="modal-close btn-flat">Cancel</button>
                </div>
            </div>
        </div>
    </div>
    <script src="js/main.js"></script></body>
</html>

Finally, update package.json to add a new parcel script, update the build script, and add a new alias section for Vue. The alias section points Parcel to the correct Vue file to bundle with src/public/js/main.ts.

  "scripts": {
    "clean": "rimraf dist/*",
    "copy-assets": "ts-node tools/copyAssets",
    "lint": "tslint -c tslint.json -p tsconfig.json --fix",
    "tsc": "tsc",
    "parcel": "parcel build src/public/js/main.ts -d dist/public/js",
    "build": "npm-run-all clean lint tsc copy-assets parcel",
    "dev:start": "npm-run-all build start",
    "dev": "nodemon --watch src -e ts,ejs --exec npm run dev:start",
    "start": "node .",
    "initdb": "ts-node tools/initdb",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "alias": {
    "vue": "./node_modules/vue/dist/vue.common.js"
  },

Now, restart the build and take your new web application for a spin!

npm run dev

Learn More About Node and TypeScript

This tutorial only scratches the surface of what you can do with Node.js and TypeScript. Below are more resources to explore.

• TypeScript Learning Resources by Jonathan Creamer
• TypeScript Node Starter - an open-source project by Microsoft
• TypeScript Deep Dive - Free online book by Basarat Ali Syed
• TypeScript Documentation
• Vue TypeScript Support
• Simple Node Authentication

You can find the completed Guitar Inventory project on GitHub.

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