TypeScript

TypeScript is a superset of JavaScript which primarily provides optional static typing, classes and interfaces. One of the big benefits is to enable IDEs to provide a richer environment for spotting common errors as you type the code.

Instead of only adding types to standard JavaScript like flow does TypeScript is a language of its own. It is aimed for large projects to get more robust software, while still being deployable as regular JavaScript.

I for myself find TypeScript better supported, better community and faster developing so after my first steps with flow+babel I switched to TypeScript.

0.1. Installation

First you need to install TypeScript:

$ npm install typescript ts-node @types/node --save-dev

To make it usable you also have to add a configuration file tsconfig.json in your project root:

{
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "outDir": "dist",
    "declaration": true,
    "sourceMap": true,
    "removeComments": true,
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true,
    "noImplicitThis": true,
    "alwaysStrict": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true
  },
  "files": [
    "./node_modules/@types/mocha/index.d.ts",
    "./node_modules/@types/node/index.d.ts"
  ],
  "include": [
    "src/**/*.ts"
  ],
  "exclude": [
    "node_modules"
  ]
}

0.2. Usage

Now you can integrate it in your package.json:

{
  "scripts": {
    "lint": "tslint -c tslint.json 'src/**/*.ts'",
    "test": "mocha -r ts-node/register test/mocha/**.ts",
    "coverage": "nyc mocha",
    "dev": "NODE_ENV=development nodemon --exec ./node_modules/.bin/ts-node -- ./src/index.ts",
    "build": "tsc",
    "start": "node dist/index",
    "prepublish": "npm run build"
  },
  "engines": {
    "node": ">=6"
  }  
}

Also specify the engines information to help people use your module in the right version.

This defines the transformation to:

1. Be used as JIT compiler in dev mode (run using npm run dev)
2. Be converted into ES6 code by running npm run build (into dist folder)
3. Everything in dist folder can be used without TypeScript
4. Before publishing to npm the build command is called automatically