TypeScript Tips

Make bugs impossible.
One TypeScript tip at a time.

I like the tricks :) – Kasia

Numbers with units (2)

@RiccardoOdone • Suggest a tip •

You can brand types to distinguish one from the other. Though, if you need to prevent combining types, branding is not a good solution.

const height: number = 2
const weight: number = 3

const format = (height: number, weight: number): string => ""

format(weight, height) // ⛔️ Swapped

declare const brand: unique symbol;
type Brand<Type, Brand> = Type & { readonly [brand]: Brand }

type Height = Brand<number, "Height">
type Weight = Brand<number, "Weight">

const height = 2 as Height
const weight = 3 as Weight

const format = (height: Height, weight: Weight): string => ""

format(weight, height) // ✅ Does not compile
weight + height // ⛔️ Do not use branding if need combining
Type-safe carousel Do not throw Filter using a type assertion Use precise types Type-safe string templating Enumerating a union type Numbers with units Zero null Enumerating statuses And types Avoiding window as any Use descriptive values Check authorization with types Extract union types from record types Keep in sync with conditional types Type-safe pick Pass arguments by name Pick instead of duplicating Prevent mutations Type aliases Model with different types Prefer static types over tests Push conditionals down Type-level functions Check Authorization With Types (again) From Union to Tuple Limit types Laser-focused types Callable types Partial considered harmful Satisfy types WTH?! Parse, don't cast Narrow types Fetch footgun Model with different types (2) Polymorphic types Parse, don't cast (again) Type-safe env Object vs Record const Type Parameters Dig Type checks Expand intellisense Numbers with units (2) Unchecked indexed access

TypeScript Tips

Crafted with 💛 by Riccardo