cefn

/** Stricter keyof */
export type RecordKey<T> = T extends Partial<infer R> ? (R extends Record<infer K, unknown> ? K : never) : never;

/** Stricter type for members of Object.entries(t) */
export type RecordEntry<T> = { [K in RecordKey<T>]: [K, Required<T>[K]] }[RecordKey<T>];

/** Type-narrowed equivalent of Object.entries */
export function entries<T extends Readonly<NonNullable<{}>>>(obj: T) {
  return Object.entries(obj) as RecordEntry<T>[];
}

cefn

/** The union of the types of members of array `Arr` */
export type MemberOf<Arr extends readonly unknown[]> = Arr[number];

// from https://stackoverflow.com/a/65914848/2257198
type Tuple<T, N extends number, A extends unknown[] = []> = A extends { length: N } ? A : Tuple<T, N, [...A, T]>;

export function composeTuple<Item, Length extends number, LengthCast = [...Item[]]>(item: Item, length: Length) {
  return Array.from({ length }).map(() => item) as LengthCast;
}

cefn

export function decorateSequence<
  G extends Generator<Yielded>,
  Yielded,
  Decorated
>(
  generator: G,
  decorate: (yielded: Yielded) => Decorated
): Generator<Decorated, GReturned<G>, GNexted<G>> {
  function mapResult(
    result: IteratorResult<Yielded, GReturned<G>>

cefn

type Passage = string;

async function tell(passage: Passage): Promise<void> {}

async function choose<Choice extends string>(
  passage: Passage,
  choices: Record<Choice, Passage>
): Promise<Choice> {
  return Object.keys(choices)[0] as Choice;
}

cefn

export type Returned<
  G extends Generator<any, any, any> | AsyncGenerator<any, any, any>
> = G extends Generator<any, infer TReturn, any>
  ? TReturn
  : G extends AsyncGenerator<any, infer AsycTReturn, any>
  ? AsycTReturn
  : never;

cefn

export type Yielded<
  G extends Generator<any, any, any> | AsyncGenerator<any, any, any>
> = G extends Generator<infer T, any, any>
  ? T
  : G extends AsyncGenerator<infer AsyncT, any, any>
  ? AsyncT
  : never;

cefn

type IndexOf<T extends {length: number}> = Exclude<Partial<T>["length"], T['length']> & number;

cefn

function waitableJestFn<Result, Args extends any[]>(
  implementation?: (...args: Args) => Result,
) {
  const mock = jest.fn<Result, Args>(implementation);
  const asyncMethods = {
    waitForCallback: (count = 1) =>
      new Promise<Args>((resolve) => {
        mock.mockImplementation(((...args) => {
          count--;
          if (count === 0) resolve(args);

cefn

import { computed, ComputedRef } from 'vue';

export function followDescendantsByName<
  ReactiveParent,
  ChildKeys extends ReadonlyArray<keyof ReactiveParent>,
>(parentSelector: () => ReactiveParent, childKeys: ChildKeys) {
  return Object.fromEntries(
    childKeys.map((childKey) => {
      return [childKey, computed(() => parentSelector()[childKey])];
    }),

cefn

import * as dotenv from 'dotenv';

dotenv.config();

const VARS = {
  API_TOKEN: 'an API token',
  API_URL: 'a URL for an endpoint',
} as const;

for (const [varname, description] of Object.entries(VARS)) {