02-hello-world.md

Hello World

Start project

mkdir -p typescript-hello-world/src
cd typescript-hello-world
yarn init
cat package.json

Set the .nvmrc

nvm current > .nvmrc

Add TypeScript

yarn add --dev typescript
yarn add --dev @types/node # all typings for node
yarn add --dev @tsconfig/node14 # recommend settings if we know what version of node we are targetting.

These are all dev-dependencies. Once our code has transpiled to JavaScript, these dependencies are not required to run.

Setup tsconfig.json

cat << EOF > tsconfig.json
{
  "extends": "@tsconfig/node14/tsconfig.json",
  "compilerOptions": {
    "outDir": "dist",
    "noEmitOnError": true // don't transpile the code if there's an error
  },
  "include": [
    "./src/**/*.ts"
  ]
}
EOF

Hello world

Within src, create index.ts with :

cat << EOF > src/index.ts
console.log("Hello World!");
EOF

rimraf

Just think of this as just rm -f but will work in all operating system

yarn add --dev rimraf

Create some scripts in package.json

{
  // ---
  "scripts": {
    "build": "rimraf dist && tsc --project tsconfig.json",
    "start": "node dist/index.js"
  },
  // ---
}

Run !

yarn install # or just yarn
yarn build
yarn start