Add TypeScript definition (#21)

index.d.ts

@@ -0,0 +1,202 @@
+/// <reference lib="esnext"/>
+
+export type AddRemoveListener<FirstArgumentType, RestArgumentsType> = (
+	event: string | symbol,
+	listener: (
+		firstArgument: FirstArgumentType,
+		...rest: RestArgumentsType[]
+	) => void
+) => void;
+
+export interface Emitter<EmittedType, EmittedTypeRest> {
+	on?: AddRemoveListener<EmittedType, EmittedTypeRest>;
+	addListener?: AddRemoveListener<EmittedType, EmittedTypeRest>;
+	addEventListener?: AddRemoveListener<EmittedType, EmittedTypeRest>;
+	off?: AddRemoveListener<EmittedType, EmittedTypeRest>;
+	removeListener?: AddRemoveListener<EmittedType, EmittedTypeRest>;
+	removeEventListener?: AddRemoveListener<EmittedType, EmittedTypeRest>;
+}
+
+export type FilterFunction<ElementType> = (element: ElementType) => boolean;
+
+export interface CancelablePromise<ResolveType> extends Promise<ResolveType> {
+	cancel(): void;
+}
+
+/**
+ * Promisify an event by waiting for it to be emitted.
+ *
+ * @param emitter - Event emitter object. Should have either a `.on()`/`.addListener()`/`.addEventListener()` and `.off()`/`.removeListener()`/`.removeEventListener()` method, like the [Node.js `EventEmitter`](https://nodejs.org/api/events.html) and [DOM events](https://developer.mozilla.org/en-US/docs/Web/Events).
+ * @param event - Name of the event or events to listen to. If the same event is defined both here and in `rejectionEvents`, this one takes priority. **Note**: `event` is a string for a single event type, for example, `'data'`. To listen on multiple events, pass an array of strings, such as `['started', 'stopped']`.
+ * @returns A `Promise` that is fulfilled when emitter emits an event matching `event`, or rejects if emitter emits any of the events defined in the `rejectionEvents` option. The returned promise has a `.cancel()` method, which when called, removes the event listeners and causes the promise to never be settled.
+ */
+declare function pEvent<EmittedType, EmittedTypeRest = EmittedType>(
+	emitter: Emitter<EmittedType, EmittedTypeRest>,
+	event: string | symbol | (string | symbol)[],
+	options: MultiArgumentsOptions<EmittedType | EmittedTypeRest>
+): CancelablePromise<(EmittedType | EmittedTypeRest)[]>;
+declare function pEvent<EmittedType>(
+	emitter: Emitter<EmittedType, unknown>,
+	event: string | symbol | (string | symbol)[],
+	filter: FilterFunction<EmittedType>
+): CancelablePromise<EmittedType>;
+declare function pEvent<EmittedType>(
+	emitter: Emitter<EmittedType, unknown>,
+	event: string | symbol | (string | symbol)[],
+	options?: Options<EmittedType>
+): CancelablePromise<EmittedType>;
+
+export default pEvent;
+
+/**
+ * Wait for multiple event emissions. Returns an array.
+ */
+export function multiple<EmittedType, EmittedTypeRest = EmittedType>(
+	emitter: Emitter<EmittedType, EmittedTypeRest>,
+	event: string | symbol | (string | symbol)[],
+	options: MultipleMultiArgumentsOptions<EmittedType | EmittedTypeRest>
+): CancelablePromise<(EmittedType | EmittedTypeRest)[][]>;
+export function multiple<EmittedType>(
+	emitter: Emitter<EmittedType, unknown>,
+	event: string | symbol | (string | symbol)[],
+	options: MultipleOptions<EmittedType>
+): CancelablePromise<EmittedType[]>;
+
+/**
+ * @returns An [async iterator](http://2ality.com/2016/10/asynchronous-iteration.html) that lets you asynchronously iterate over events of `event` emitted from `emitter`. The iterator ends when `emitter` emits an event matching any of the events defined in `resolutionEvents`, or rejects if `emitter` emits any of the events defined in the `rejectionEvents` option.
+ */
+export function iterator<EmittedType, EmittedTypeRest = EmittedType>(
+	emitter: Emitter<EmittedType, EmittedTypeRest>,
+	event: string | symbol | (string | symbol)[],
+	options: IteratorMultiArgumentsOptions<EmittedType | EmittedTypeRest>
+): AsyncIterableIterator<(EmittedType | EmittedTypeRest)[]>;
+export function iterator<EmittedType>(
+	emitter: Emitter<EmittedType, unknown>,
+	event: string | symbol | (string | symbol)[],
+	filter: FilterFunction<EmittedType>
+): AsyncIterableIterator<EmittedType>;
+export function iterator<EmittedType>(
+	emitter: Emitter<EmittedType, unknown>,
+	event: string | symbol | (string | symbol)[],
+	options?: IteratorOptions<EmittedType>
+): AsyncIterableIterator<EmittedType>;
+
+export interface Options<EmittedType> {
+	/**
+	 * Events that will reject the promise.
+	 *
+	 * @default ['error']
+	 */
+	rejectionEvents?: (string | symbol)[];
+
+	/**
+	 * By default, the promisified function will only return the first argument from the event callback, which works fine for most APIs. This option can be useful for APIs that return multiple arguments in the callback. Turning this on will make it return an array of all arguments from the callback, instead of just the first argument. This also applies to rejections.
+	 *
+	 * @default false
+	 *
+	 * @example
+	 *
+	 * const pEvent = require('p-event');
+	 * const emitter = require('./some-event-emitter');
+	 *
+	 * (async () => {
+	 *    const [foo, bar] = await pEvent(emitter, 'finish', {multiArgs: true});
+	 * })();
+	 */
+	multiArgs?: boolean;
+
+	/**
+	 * Time in milliseconds before timing out.
+	 *
+	 * @default Infinity
+	 */
+	timeout?: number;
+
+	/**
+	 * Filter function for accepting an event.
+	 *
+	 * @example
+	 *
+	 * const pEvent = require('p-event');
+	 * const emitter = require('./some-event-emitter');
+	 *
+	 * (async () => {
+	 *     const result = await pEvent(emitter, '🦄', value => value > 3);
+	 *     // Do something with first 🦄 event with a value greater than 3
+	 * })();
+	 */
+	filter?: FilterFunction<EmittedType>;
+}
+
+export interface MultiArgumentsOptions<EmittedType>
+	extends Options<EmittedType> {
+	multiArgs: true;
+}
+
+export interface MultipleOptions<EmittedType> extends Options<EmittedType> {
+	/**
+	 * The number of times the event needs to be emitted before the promise resolves.
+	 */
+	count: number;
+
+	/**
+	 * Whether to resolve the promise immediately. Emitting one of the `rejectionEvents` won't throw an error.
+	 *
+	 * **Note**: The returned array will be mutated when an event is emitted.
+	 *
+	 * @example
+	 *
+	 * const emitter = new EventEmitter();
+	 *
+	 * const promise = multiple(emitter, 'hello', {
+	 *     resolveImmediately: true,
+	 *     count: Infinity
+	 * });
+	 *
+	 * const result = await promise;
+	 * console.log(result);
+	 * //=> []
+	 *
+	 * emitter.emit('hello', 'Jack');
+	 * console.log(result);
+	 * //=> ['Jack']
+	 *
+	 * emitter.emit('hello', 'Mark');
+	 * console.log(result);
+	 * //=> ['Jack', 'Mark']
+	 *
+	 * // Stops listening
+	 * emitter.emit('error', new Error('😿'));
+	 *
+	 * emitter.emit('hello', 'John');
+	 * console.log(result);
+	 * //=> ['Jack', 'Mark']
+	 */
+	resolveImmediately?: boolean;
+}
+
+export interface MultipleMultiArgumentsOptions<EmittedType>
+	extends MultipleOptions<EmittedType> {
+	multiArgs: true;
+}
+
+export interface IteratorOptions<EmittedType> extends Options<EmittedType> {
+	/**
+	 * Maximum number of events for the iterator before it ends. When the limit is reached, the iterator will be marked as `done`. This option is useful to paginate events, for example, fetching 10 events per page.
+	 *
+	 * @default Infinity
+	 */
+	limit?: number;
+
+	/**
+	 * Events that will end the iterator.
+	 *
+	 * @default []
+	 */
+	resolutionEvents?: (string | symbol)[];
+}
+
+export interface IteratorMultiArgumentsOptions<EmittedType>
+	extends IteratorOptions<EmittedType> {
+	multiArgs: true;
+}

index.js

@@ -93,7 +93,7 @@ const multiple = (emitter, event, options) => {
 	return ret;
 };
 
-module.exports = (emitter, event, options) => {
+const pEvent = (emitter, event, options) => {
 	if (typeof options === 'function') {
 		options = {filter: options};
 	}
@@ -111,6 +111,9 @@ module.exports = (emitter, event, options) => {
 	return promise;
 };
 
+module.exports = pEvent;
+module.exports.default = pEvent;
+
 module.exports.multiple = multiple;
 
 module.exports.iterator = (emitter, event, options) => {

index.test-d.ts

@@ -0,0 +1,126 @@
+/// <reference types="node"/>
+
+import {expectType} from 'tsd-check';
+import pEvent, {multiple, iterator, CancelablePromise} from '.';
+import {EventEmitter} from 'events';
+import * as fs from 'fs';
+
+class NodeEmitter extends EventEmitter {
+	on(event: 'finish', listener: (number: number, string: string) => void) {
+		return this;
+	}
+	addListener(
+		event: 'finish',
+		listener: (number: number, string: string) => void
+	) {
+		return this;
+	}
+	addEventListener(
+		event: 'finish',
+		listener: (number: number, string: string) => void
+	) {
+		return this;
+	}
+	off(event: 'finish', listener: (number: number, string: string) => void) {
+		return this;
+	}
+	removeListener(
+		event: 'finish',
+		listener: (number: number, string: string) => void
+	) {
+		return this;
+	}
+	removeEventListener(
+		event: 'finish',
+		listener: (number: number, string: string) => void
+	) {
+		return this;
+	}
+}
+
+class DomEmitter implements EventTarget {
+	addEventListener(
+		type: 'foo',
+		listener: EventListenerOrEventListenerObject,
+		options?: boolean | AddEventListenerOptions
+	): void {}
+
+	dispatchEvent(event: Event): boolean {
+		return false;
+	}
+
+	removeEventListener(
+		type: 'foo',
+		listener: EventListenerOrEventListenerObject,
+		options?: boolean | AddEventListenerOptions
+	): void {}
+}
+
+expectType<CancelablePromise<number>>(pEvent(new NodeEmitter(), 'finish'));
+expectType<CancelablePromise<number>>(
+	pEvent(new NodeEmitter(), '🦄', value => value > 3)
+);
+expectType<CancelablePromise<Event>>(pEvent(new DomEmitter(), 'finish'));
+expectType<CancelablePromise<Event>>(pEvent(document, 'DOMContentLoaded'));
+
+expectType<CancelablePromise<number>>(
+	pEvent(new NodeEmitter(), 'finish', {rejectionEvents: ['error']})
+);
+expectType<CancelablePromise<number>>(
+	pEvent(new NodeEmitter(), 'finish', {timeout: 1})
+);
+expectType<CancelablePromise<number>>(
+	pEvent(new NodeEmitter(), 'finish', {filter: value => value > 3})
+);
+expectType<CancelablePromise<(string | number)[]>>(
+	pEvent(new NodeEmitter(), 'finish', {multiArgs: true})
+);
+
+pEvent(new NodeEmitter(), 'finish').cancel();
+
+expectType<CancelablePromise<number[]>>(
+	multiple(new NodeEmitter(), 'hello', {count: Infinity})
+);
+expectType<CancelablePromise<number[]>>(
+	multiple(new NodeEmitter(), 'hello', {
+		resolveImmediately: true,
+		count: Infinity
+	})
+);
+expectType<CancelablePromise<(string | number)[][]>>(
+	multiple(new NodeEmitter(), 'hello', {
+		count: Infinity,
+		multiArgs: true
+	})
+);
+
+expectType<AsyncIterableIterator<number>>(
+	iterator(new NodeEmitter(), 'finish')
+);
+expectType<AsyncIterableIterator<number>>(
+	iterator(new NodeEmitter(), '🦄', value => value > 3)
+);
+
+expectType<AsyncIterableIterator<number>>(
+	iterator(new NodeEmitter(), 'finish', {limit: 1})
+);
+expectType<AsyncIterableIterator<number>>(
+	iterator(new NodeEmitter(), 'finish', {resolutionEvents: ['finish']})
+);
+expectType<AsyncIterableIterator<(string | number)[]>>(
+	iterator(new NodeEmitter(), 'finish', {multiArgs: true})
+);
+
+async function getOpenReadStream(file: string) {
+	const stream = fs.createReadStream(file);
+	await pEvent(stream, 'open');
+	return stream;
+}
+
+const stream = await getOpenReadStream('unicorn.txt');
+stream.pipe(process.stdout);
+
+const result = await pEvent(new NodeEmitter(), 'finish');
+if (result === 1) {
+	throw new Error('Emitter finished with an error');
+}

package.json

@@ -13,10 +13,11 @@
 		"node": ">=8"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd-check"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"promise",
@@ -45,8 +46,10 @@
 		"p-timeout": "^2.0.1"
 	},
 	"devDependencies": {
+		"@types/node": "^11.9.5",
 		"ava": "^1.2.1",
 		"delay": "^4.1.0",
+		"tsd-check": "^0.3.0",
 		"xo": "^0.24.0"
 	}
 }