// 1. install Node.js & check
node --version // 14.15.4 (as of 2021)
// 2. install npm (along with Node.js) & check
npm --version // 6.14.10
// 3. install Git (optional) & check
git --version // 2.30.0
// 4. install TypeScript & check
npm install --global typescript@4.2.2
tsc --version // 4.2.2
// when type not specified, compiler will default to `any`.
noImplicitAny = on
// check null or undefined
strictNullChecks = on