Why typesystem?

A type system is a restriction. A good restriction
- Think of Rust
Type system application
- Compile time validation
- IDE intellisense
- Static analysis
- Reflection
- Compile time optimization (less relevant for Typescript)
  - There is Google closure compiler (for js with js docs)

Typescript features

Typescript is structural

Strict null check

tsconfig.json flag
null and undefined are separate types
operator ?? and ?=

⇒ never call methods of null again!

Union type

literals are also types
restrict the acceptable values

Narrowing union types

Typeof and instanceof
Control flow analysis
Discriminated union
Type guard and assert function

Type manipulation

(Demo only as it is very long)

TODO demo

Typescript library

Showcase only

Type helper

Definitelytyped

Microsoft-maintained repo with types for js libraries that do not have typing

ts-essentials

Type utilities

ts toolbelt

ts-essentials but bigger

Runtime validator

Zod

arktype

Metaprogramming

Meta-types

Arithmetic and logic calculation with literal types

HOTscript

Functional programming but with types

Typescript tool

typescript-eslint

More linting rule for typescript

Typerunner

tsc alternative, written in C++