This Pattern Will Wreck Your React App's TS Performance
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. A couple of years ago, Sentry were having big problems with their React app. They'd pretty recently migrated it to TypeScript from JavaScript. And the app was part of a large monorepo. But the IDE performance was slow. You'd often need to wait a couple of seconds after making a chan
Type Predicate Inference: The TS 5.5 Feature No One Expected
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. TypeScript 5.5 will be dropping in the next couple of months. And thanks to one PR in particular, I already know it's going to be an incredible release. On Friday night, TypeScript merged Dan Vanderkam's PR to "Infer type predicates from function bodies using control flow analysis".
You Can't Make Children "Type Safe" in React & TypeScript
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. If you've worked with TypeScript and JSX for enough time, you'll probably have run into a situation where you want to restrict a component's children to be of a certain type. Let's say you're working on a Select component that takes Option components as children. You want to make su
How To Type Array.reduce
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. There's a common issue that comes up whenever you try to use Array.reduce to transform an array into an object. Learning how to fix it can teach you a lot about how to handle Array.reduce in general. Here's a playground: see if you can fix the error in the code below. #Why Is The Er
The TSConfig Cheat Sheet
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. tsconfig.json scares everyone. It's a huge file with a TON of potential options. But really, there are only a few configuration options you need to care about. Let's figure them out, and cheatsheet them. #Quickstart Want just the code? Here you go:
Method Shorthand Syntax Considered Harmful
Using the method shorthand syntax for function annotations in TypeScript can result in runtime errors. It is recommended to use object property syntax instead.
TS Reset - Official Docs
without ts-reset🚨 .json (in fetch) and JSON.parse both return any🤦 .filter(Boolean) doesn't behave how you expect😡 array.includes often breaks on readonly arrays with ts-reset👍 .json (in fetch) and JSON.parse return unknown✅ .filter(Boolean) behaves EXACTLY how you expect🥹 array.includes is widened to be more ergonomic🚀 And several more improvements!
Type vs Interface: Which Should You Use?
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. #Quick Explanation You should use types by default until you need a specific feature of interfaces, like 'extends'. Interfaces can't express unions, mapped types, or conditional types. Type aliases can express any type. Interfaces can use extends, types can't. When you're working wi
Strongly Type useRef with ElementRef
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. Using useRef with native elements can be a bit of a pain. You need to specify the type of the element you're targeting, but it's not always clear what type you should be using.
Type Argument Placeholders: TypeScript's Most Discussed Upcoming Feature
←All ArticlesType Argument Placeholders: TypeScript's Most Discussed Upcoming Feature Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. #Quick Explanation TypeScript 5.2 introduces type argument placeholders, which let you pass a _ to a type argument to allow it to infer the type instead of using its default. // The underscores tel
The Empty Object Type in TypeScript
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. #Quick Explanation The empty object type - {} - doesn't behave how you expect in TypeScript. Instead of representing an empty object, it represents any value except null and undefined. This is because TypeScript's type system is structural, not nominal. Everything except null and un
Since TypeScript 5.1, React.FC is now "fine"
Matt PocockMatt is a well-regarded TypeScript expert known for his ability to demystify complex TypeScript concepts. #Quick Breakdown As of TypeScript 5.1 and React 18, React.FC is now officially 'fine'. It no longer implicitly includes children in the props type. It no longer breaks if you return undefined, string, or number. I still recommend simply annotating props instead of using React.FC. Bu
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When 'as never' Is The Only Thing That Works
What's Coming In TypeScript 5.3?