#MappedTypes
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morfes.bsky.social
Mapped types: transform generic object keys into new types using key mapping and template literals. Recursively create new signatures per object key. Enables scalable, type-safe contracts at the type level. (see image)

#TypeScript #StaticTyping #MappedTypes
type Signal<T extends object> = T & { onChange: (callback: Callback<T>) => () => void; } & { [K in keyof T as `on${Capitalize<string & K>}Change`]: (callback: (value: T[K], oldValue: T[K]) => void) => () => void; } & { [K in keyof T as `${string & K}AsSignal`]: T[K] extends object ? Signal<T[K]> : Signal<{value: T[K]}>; }
August 6, 2025 at 4:54 AM
omid.dev
Deep Dive into Advanced TypeScript: Conditional Types, Mapped Types, and Recursive Types
g.omid.dev/ZVEdZo5
#TypeScript #Types #MappedTypes #RecursiveTypes #ConditionalTypes #Developers
Deep Dive into Advanced TypeScript: Conditional Types, Mapped Types, and Recursive Types
TypeScript has transformed the way we write JavaScript by providing a static type system that helps developers catch errors early and write more robust code. While basic types and interfaces cover a s...
g.omid.dev
June 14, 2024 at 1:00 PM
morfes.bsky.social
With TypeScript’s infer and mapped types, you can extract hidden types to make type-safe helpers for ORMs instead of using any. This helps create safer, smarter filter params. #TypeScript #infer #MappedTypes #TypeSafety #ORM #DevTips
// typeorm type userFilter = MyParameters<User.find> const foo = (arg1: string, arg2: number): void => { } type MyParameters<T extends (...args: any[]) => any> = T extends (...args: infer P) => any ? P : never; type FunctionParamsType = MyParameters<typeof foo> // [arg1: string, arg2: number]
August 6, 2025 at 5:03 PM