Typescript utilities

utilities.types.ts

import "@total-typescript/ts-reset";

export {}

// Makes all properties optional
export type DeepPartial<T> = T extends object
  ? {
      [P in keyof T]?: DeepPartial<T[P]>
    }
  : T

// Type with only selected properties
export type Only<T, U> = {
  [P in keyof T]: T[P]
} & {
  [P in keyof U]?: never
}

// One or the other
export type Either<T, U> = Only<T, U> | Only<U, T>

// Allow array.filter(Boolean), already handled in
// https://github.com/total-typescript/ts-reset
type Falsy = false | 0 | '' | null | undefined
interface Array<T> {
  filter<S extends T>(
    predicate: BooleanConstructor,
    thisArg?: any
  ): Exclude<S, Falsy>[]
}

// Make chosen fields required. Useful when fetching data that
// has different relations loaded in different endpoints
export type WithRequired<TType, TRequiredKeys extends keyof TType> = TType & {
  [P in TRequiredKeys]-?: TType[P]
}