TypeScriptin kääntäminen JavaScriptiksi

npm install --save-dev typescript
npx tsc --version

// hello.ts
function greet(name: string): string {
  return 'Hello, ' + name;
}
console.log(greet('World'));

// Compile: npx tsc hello.ts
// Output: hello.js (no types)

npx tsc --init
// Creates tsconfig.json with defaults and comments

{
  "compilerOptions": {
    "target": "ES2020",
    "module": "commonjs",
    "outDir": "./dist",
    "strict": true
  }
}

npx tsc --watch
// Watches for changes and recompiles on save

// tsconfig.json
{ "compilerOptions": { "noEmit": true } }

// Then run:
npx tsc --noEmit

# Run TS directly with ts-node
npx ts-node src/index.ts

# Or faster with tsx
npx tsx src/index.ts

{ "compilerOptions": { "sourceMap": true } }

{ "compilerOptions": { "declaration": true } }
// Outputs: dist/index.js AND dist/index.d.ts

{ "compilerOptions": { "noEmitOnError": true } }