Run Scripts

1. Install ts-node

npm install -D ts-node

2. Create and Run a Script File

console.log("Hello world");

Run the script

npx ts-node scripts/hello.ts

or

npx ts-node --transpile-only scripts/hello.ts

What is --transpile-only?

• Skips type checking.
• Only converts (transpiles) your .ts code to JavaScript and runs it immediately.
• Faster, fewer errors, but won’t catch TypeScript mistakes.
• Great for quick scripts, setup utilities, or anything you just want to run now.

When you don't put ---transpile-only:

• Does full type checking before running.
• Slower to start but safer, it’ll stop execution if TypeScript finds an error.
• Great for production or when you want to enforce type safety.

3. Use dotenv

The dotenv library loads variables from a .env file into process.env, letting your script access settings or secrets without manually setting them in the terminal. We can also use .env.local but we have to specify it in the script as you will see shortly.

npm install dotenv

Create environment variable to test

GREETING=HelloWorld

Modify hello.ts to use dotenv in the script

import dotenv from "dotenv";
dotenv.config({ path: ".env.local" });
 
console.log(process.env.GREETING);

4. Create Custom TypeScript Configuration

At this point, you can’t run the script yet because it now relies on dotenv. To fix this, create a custom TypeScript configuration file named tsconfig.scripts.json. The purpose of this file is to provide a separate TypeScript setup for running standalone Node scripts, ensuring they work independently from Next.js’s default tsconfig.json (which is configured for browser builds and often incompatible with ts-node).

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "commonjs",
    "esModuleInterop": true,
    "skipLibCheck": true,
    "strict": false
  },
  "include": ["scripts/**/*.ts"]
}

Now you can run the script as follows:

npx ts-node --project tsconfig.scripts.json scripts/hello.ts

5. Modify package.json

To make running scripts easier, we will modify our package.json to include a custom npm command. This way, you don’t have to type out the full command and reference tsconfig.scripts.json every time.

  "scripts": {
    ...
    "run-script": "ts-node --project tsconfig.scripts.json"
  },

Now you can run any scripts using the following format:

npm run run-script -- scripts/hello.ts