Promises

Utilities for working with promises.

promiseMap

Takes an object of promises and resolves them in parallel, returning an object with the same keys and resolved values. A more ergonomic alternative to Promise.all with array destructuring.

import { promiseMap } from '@repo/utils'

function promiseMap<T extends Record<string, unknown>>(
  input: { [K in keyof T]: MaybePromise<T[K]> }
): Promise<T>

Example

import { promiseMap } from '@repo/utils'

// Instead of:
const [user, posts, settings] = await Promise.all([
  fetchUser(id),
  fetchPosts(id),
  fetchSettings(id),
])

// Write:
const { user, posts, settings } = await promiseMap({
  user: fetchUser(id),
  posts: fetchPosts(id),
  settings: fetchSettings(id),
})

Works with mixed promise and non-promise values:

import { promiseMap } from '@repo/utils'

const result = await promiseMap({
  data: fetchData(),       // Promise
  label: 'static value',  // plain value
})
// result.data -- resolved value
// result.label -- 'static value'

isPromise

Checks if a value is a Promise by verifying it has .then() and .catch() methods.

import { isPromise } from '@repo/utils'

function isPromise(value: unknown): boolean

Example

import { isPromise } from '@repo/utils'

isPromise(Promise.resolve(42))    // true
isPromise(fetch('/api'))          // true
isPromise(42)                     // false
isPromise(null)                   // false
isPromise({ then: () => {} })     // false (missing .catch)