Deploying a Node.js Application Using TypeScript on Heroku

Introduction

When deploying a Node.js application written in TypeScript to platforms like Heroku, developers often encounter challenges with file extensions and module compatibility. This tutorial will guide you through the process of successfully deploying a Node.js application using TypeScript on Heroku by addressing common issues related to unknown file extensions, such as ".ts". We’ll explore solutions involving ts-node, tsx, and configuration adjustments in both package.json and tsconfig.json.

Understanding the Problem

When you attempt to deploy a TypeScript application with .ts files directly, you may encounter errors like "Unknown file extension ‘.ts’". This occurs because Node.js, by default, does not understand the TypeScript file extensions. The error typically surfaces during deployment on platforms like Heroku when using commands such as npm start.

This tutorial will provide several approaches to resolve this issue and ensure your TypeScript application runs smoothly in a production environment.

Prerequisites

• A basic understanding of Node.js and npm.
• Familiarity with TypeScript syntax and configuration.
• A Heroku account for deployment (optional but recommended).

Solutions Overview

1. Using tsx

tsx is a tool that transpiles TypeScript files on-the-fly and works seamlessly out-of-the-box.

Installation

npm install -D tsx

Running the Application

Replace your existing start script in package.json with:

"scripts": {
  "start": "tsx src/App.ts"
}

This command will transpile and execute your TypeScript application directly. tsx has gained popularity due to its ease of use and performance.

2. Configuring ts-node with ESM

If you prefer using ts-node, ensure it’s configured correctly for ECMAScript Modules (ESM).

Adjustments in package.json

Remove or adjust the "type": "module" entry if necessary:

{
  "name": "your-app",
  "version": "1.0.0",
  "main": "dist/app.js",
  "scripts": {
    "start": "ts-node-esm src/App.ts"
  },
  "dependencies": {
    ...
  }
}

Installation

Ensure ts-node is installed:

npm install -g ts-node

Running the Application

Use the following command to start your application with ESM support:

ts-node-esm src/App.ts

Alternatively, use the Node.js loader option for experimental module resolution:

node --loader ts-node/esm src/App.ts

or

ts-node --esm src/App.ts

3. Configuration in tsconfig.json

Ensure your TypeScript configuration supports modern JavaScript features and interoperability with CommonJS modules.

Sample tsconfig.json

{
  "compilerOptions": {
    "module": "ESNext",
    "esModuleInterop": true,
    "target": "ESNext",
    "moduleResolution": "Node",
    "outDir": "dist",
    "strict": true,
    "noImplicitAny": true,
    "useUnknownInCatchVariables": false,
    "inlineSourceMap": true
  },
  "include": ["src/**/*.ts"],
  "exclude": ["node_modules", "**/*.spec.ts"]
}

Deployment on Heroku

1. Ensure your package.json includes a "start" script tailored for deployment.
2. Commit all changes and push to Heroku:

git add .
git commit -m "Prepare TypeScript app for Heroku"
git push heroku master

Heroku will build and run your application using the specified start command.

Best Practices

• Regularly update dependencies like ts-node and tsx to benefit from performance improvements and new features.
• Test your deployment process locally with a similar environment to reduce unexpected issues during production deployment.
• Monitor logs on Heroku for any runtime errors or warnings after deployment.

By following the steps outlined in this tutorial, you can effectively deploy your TypeScript-based Node.js applications on Heroku, ensuring smooth execution and scalability. Whether you choose tsx for simplicity or configure ts-node with ESM support, both approaches provide robust solutions to common deployment challenges.