add Promise.allSettled

Author: keithamus

src/index.ts

@@ -6,6 +6,7 @@ import * as cryptoRandomUUID from './crypto-randomuuid.js'
 import * as elementReplaceChildren from './element-replacechildren.js'
 import * as eventAbortSignal from './event-abortsignal.js'
 import * as objectHasOwn from './object-hasown.js'
+import * as promiseAllSettled from './promise-allsettled.js'
 import * as promiseAny from './promise-any.js'
 import * as requestIdleCallback from './requestidlecallback.js'
 
@@ -32,7 +33,7 @@ const baseSupport =
   'flatMap' in Array.prototype &&
   'trimEnd' in String.prototype &&
   // ES2020
-  'allSettled' in Promise &&
+  //'allSettled' in Promise && // Polyfilled
   'matchAll' in String.prototype &&
   // ES2021
   'replaceAll' in String.prototype &&
@@ -51,6 +52,7 @@ const polyfills = [
   elementReplaceChildren,
   eventAbortSignal,
   objectHasOwn,
+  promiseAllSettled,
   promiseAny,
   requestIdleCallback
 ]

src/promise-allsettled.ts

@@ -0,0 +1,29 @@
+export function promiseAllSettled<T extends readonly unknown[] | []>(
+  values: T
+): Promise<{-readonly [P in keyof T]: PromiseSettledResult<Awaited<T[P]>>}> {
+  return Promise.all(
+    values.map(p =>
+      // eslint-disable-next-line github/no-then
+      Promise.resolve(p).then(
+        (value: unknown) => ({status: 'fulfilled', value}),
+        (reason: unknown) => ({status: 'rejected', reason})
+      )
+    )
+  ) as unknown as Promise<{-readonly [P in keyof T]: PromiseSettledResult<Awaited<T[P]>>}>
+}
+
+/*#__PURE__*/
+export function isSupported(): boolean {
+  return 'allSettled' in Promise && typeof Promise.allSettled === 'function'
+}
+
+/*#__PURE__*/
+export function isPolyfilled(): boolean {
+  return Promise.all === promiseAllSettled
+}
+
+export function apply(): void {
+  if (!isSupported()) {
+    Promise.allSettled = promiseAllSettled
+  }
+}

test/promise-allsettled.js

@@ -0,0 +1,23 @@
+import {apply, isPolyfilled, isSupported, promiseAllSettled} from '../lib/promise-allsettled.js'
+
+describe('Promise.allSettled', () => {
+  it('has standard isSupported, isPolyfilled, apply API', () => {
+    expect(isSupported).to.be.a('function')
+    expect(isPolyfilled).to.be.a('function')
+    expect(apply).to.be.a('function')
+    expect(isSupported()).to.be.a('boolean')
+    expect(isPolyfilled()).to.equal(false)
+  })
+
+  it('returns list of Promise value/rejections', async () => {
+    expect(
+      // eslint-disable-next-line prefer-promise-reject-errors
+      await promiseAllSettled([Promise.resolve(1), Promise.reject(2), Promise.resolve(3), Promise.reject(4)])
+    ).to.eql([
+      {status: 'fulfilled', value: 1},
+      {status: 'rejected', reason: 2},
+      {status: 'fulfilled', value: 3},
+      {status: 'rejected', reason: 4}
+    ])
+  })
+})