Sun 31 December 2023 ) are common in Java and considered a best practice. But they're a code smell that's best avoided in JavaScript and TypeScript because the problem they solve in Java does not exist in JS/TS. This post looks at what that problem is and how you can solve it in TypeScript without imposing the boilerplate of getters and setters ..read more

Back in 2020 I gave a whole series of talks at companies that were interested in the language and the book. The talk that I gave at Etsy in December of 2020 was one of the most fun. It was recorded and is now available to watch. It's about an hour ..read more

Type guards are a powerful tool for improving TypeScript's built-in control flow analysis. This post looks at when it's appropriate to use a type predicate, and in particular what it means when a type predicate returns ..read more

Use Source Maps to Debug TypeScript ..read more

Use Functional Constructs and Libraries to Help Types Flow Functions Instead of Callbacks for Asynchronous Code ..read more

Wed 29 November 2023 keyword can infer quite a bit more than you might expect. It's extremely effective at extracting types from the sort of nested structures that you might get from codegen or an API specification ..read more

I cut one item from Effective TypeScript during the final stages of editing. Four years later, it's time for it to see the light of day! It's a trick for specializing generic types for certain subtypes of their type parameters. This post shows how it works, why it's indispensible for wrapper types, and also explains why I cut it from the book ..read more

This post looks at the Closure Compiler, Google's tool from the mid-2000s for adding types to JavaScript. It looks at how its focus on minification led to very different design choices than TypeScript, and how this and a few other factors led to TypeScript becoming the ubiquitous solution for JavaScript + types. The Closure Compiler represents an alternative path that JavaScript could have taken, and it gives us perspective on TypeScript as it exists today ..read more

If you develop server code with TypeScript, you'll inevitably come up against the question of how to interact with your database. There's lots of type information in your database (the structure of the tables) and it's not immediately clear how to share that type information between the DB and TypeScript. This post and its accompanying video present six ways to solve this problem and offer some advice gleaned from years of experience combining Postgres and TypeScript ..read more

Let's dive in to the strange world of type display! our types. There are often several possible ways to display the same type, and the choice can have a big impact on the usability of your library. TypeScript tries to make good decisions on its own about type display, but it also gives us a few very obscure levers by which we can control it ourselves ..read more