Author: Drew Colthorp

Your Dev Project Is a Classroom; Be Intentional about Learning

If you’re like me, you always learn something new on a project, but it’s usually incidental. Your focus is on writing code, and the learning just kind of… happens.

I’m here to tell you that you’re wasting a great opportunity. Your colleagues have a lot to teach you—and a lot to learn from you. A project team is a perfect environment for learning, but you’ll only get the full value if you’re intentional and thoughtful about it. Read more on Your Dev Project Is a Classroom; Be Intentional about Learning…

Statically Typed Data Validation with JSON Schema and TypeScript

One super common problem on TypeScript projects is figuring out how to validate data from external sources and tie that validated data to TypeScript types. In these situations, you generally have a few options:

  1. Define types and validations separately, and type them together with Type Guards.
  2. Use an internal DSL such as io-ts to build both a validator and the TypeScript type at the same time.
  3. Use an external DSL such as JSON Schema to define the validator, and derive the TypeScript type from there.

Read more on Statically Typed Data Validation with JSON Schema and TypeScript…

Flavoring: Flexible Nominal Typing for TypeScript

Recently, we’ve been making heavy use of TypeScript at Atomic Object. We love the great tooling and instant feedback we get with the language’s powerful type system. TypeScript’s structural type system gives us a lot of powerful tools for making invalid states unrepresentable, thereby pointing out bugs at compile time instead of runtime.

However, one challenge we’ve faced with TypeScript in applying this approach is how to differentiate between values that have the same shape, but mean very different things. For example, if both my Person and my BlogPost have a numeric ID, I’d really like to communicate to TypeScript that they’re not interchangeable. But a function that takes a number accepts both kinds of values.

This post will examine the challenges one might face using the usual approach to this modeling problem, and how we’ve side-stepped them with a variation on the usual technique.
Read more on Flavoring: Flexible Nominal Typing for TypeScript…

A New Redux Action Pattern for TypeScript 2.4+

In September 2016, I wrote a post about a pattern for strongly typed Redux reducers in TypeScript. Since then, the TypeScript team has been busy enhancing the language, and recent changes in TypeScript have enabled a much more natural, boilerplate-free pattern for strongly typed actions and reducers in TypeScript.
Read more on A New Redux Action Pattern for TypeScript 2.4+…

Modular, Type-safe Metadata with TypeScript

One of the humps I’ve encountered while learning TypeScript is coming to terms with a core tenet of the language—the type definitions you write only exist at compile time, not at runtime.

I’ve bumped into this a few times. Can I generate a predicate function to test for type compatibility? No—use type guards instead. Can I reflect on the properties of a type at runtime? No—with caveats. It turns out that those caveats matter a lot, and you can do some pretty powerful things with the tools TypeScript does provide. Read more on Modular, Type-safe Metadata with TypeScript…