Build

By the end of this step, you'll have a simple working program in Node!

Assignment

From the root of your repository, run npm init -y to create a new Node.js project.
Add TypeScript along with types for node:

npm install -D typescript @types/node

The -D flag installs the packages as development dependencies, which means they won't be included in your production build.

Configure TypeScript by creating a tsconfig.json file in the root of your project:

{
  "compilerOptions": {
    "baseUrl": ".",
    "target": "esnext",
    "module": "esnext",
    "rootDir": "./src",
    "outDir": "./dist",
    "strict": true,
    "moduleResolution": "Node",
    "esModuleInterop": true,
    "skipLibCheck": true
  },
  "include": ["./src/**/*.ts"],
  "exclude": ["node_modules"]
}

rootDir is where your TypeScript files are located
outDir is where your compiled JavaScript files will go (you won't modify these - they're generated from your TypeScript files)
include specifies the files to include in the compilation
exclude specifies the files to exclude from the compilation
strict enables all strict type checking options
esModuleInterop allows you to use ES module syntax
moduleResolution specifies how modules are resolved
skipLibCheck skips type checking all declaration files
baseUrl allows you to use paths relative to the project root

Configure the package.json in the root of your project:
- add "type":"module". This means we can use the ES module syntax in our project for imports and exports.
- add a build script that runs npx tsc - this will compile your TypeScript code to JavaScript.
- add a start script that runs node dist/main.js - this will start the REPL.
- add a dev script that runs a combination of the build and start scripts for convenience.

{
...
  "type": "module",
  "scripts": {
    "build": "npx tsc",
    "start": "node dist/main.js",
    "dev": "npx tsc && node dist/main.js"
  },
...
}

The npx command allows us to run the tsc command without installing TypeScript globally.

Create a new src directory to put your project - this is where your TypeScript code will live.
In src/main.ts, create a main() function:

function main() {
  console.log("Hello, world!");
}

main();

To pass off this step, from the root of your project, run:

npm run dev

If you see "Hello, world!" printed in the console, you're good to go!

Run and submit the CLI tests.