setup

npm install --save-dev tsconfig typescript
npx tsc --init

compile

npx tsc file.ts

commonjs vs ECMAScript modules

By default (with esModuleInterop false or not set) TypeScript treats CommonJS/AMD/UMD modules similar to ES6 modules. This turned out to be a mistake, but still exists by default in typescript to avoid a breaking change.

For new and existing projects you should set esModuleInterop to true. This is set automatically with npx tsc --init.