In this chapter, we will learn about "types," which is the most important concept in TypeScript. We will make it easy to understand even for beginners who ask "What is a type?" and experience it while ...

and this tells TypeScript that "yes, I really do want to turn my function into a string". But as I mentioned before, without the toString, TypeScript helpfully tells you that you have a type mismatch.

This library requires TypeScript 2.2 or later. If you require TypeScript 2.1 compatibility, version 0.2.0 of this library is the last one with support.

Say goodbye to source maps and compilation delays. By treating types as whitespace, modern runtimes are unlocking a “no-build” TypeScript that keeps stack traces accurate and workflows clean.