Where we're going we don't need JavaScript - Programming with Type Annotations

Your type system is a programming language. Learn to encode business logic directly into your types and make entire classes of bugs impossible at runtime.

#1about 2 minutes

Viewing TypeScript type annotations as a language

TypeScript's type system can be treated as its own functional, set-based programming language.

#2about 2 minutes

Mapping JavaScript syntax to TypeScript type constructs

Learn how JavaScript concepts like variables, functions, and objects correspond to type aliases, generics, and object types.

#3about 2 minutes

Understanding the set-based nature of TypeScript types

All types are fundamentally sets or unions, which simplifies operations and eliminates the need for explicit loops.

#4about 2 minutes

Building a type-level function to filter union types

A practical example demonstrates how to create a generic type that uses conditionals to filter null from a union.

#5about 3 minutes

The motivation for programming with type annotations

Using type-level programming allows you to abstract and enforce core business logic, similar to how high-level languages abstract machine code.

#6about 2 minutes

Deriving concrete types from abstract business rules

Instead of writing types manually, define core business rules as abstract types and then derive all concrete implementation types from them.

#7about 4 minutes

A practical example of a type-safe message bus

The challenge of building a type-safe message bus for a browser extension is introduced as a use case for type-level programming.

#8about 5 minutes

Using generics and keyof to enforce message contracts

The `send` and `on` methods are made type-safe by using generics, the `keyof` operator, and indexed access types derived from a central payload map.

#9about 3 minutes

The benefits of deriving types from first principles

Deriving types from a central source of truth ensures consistency and provides type-level automation across your entire project.

#10about 4 minutes

Q&A on performance, interfaces, and advanced learning

The speaker answers audience questions about runtime performance, the difference between `type` and `interface`, and how to learn advanced TypeScript patterns.