Support options object in pLimit()

Fixes #89

Author: sindresorhus

index.d.ts

@@ -51,10 +51,10 @@ export type LimitFunction = {
 /**
 Run multiple promise-returning & async functions with limited concurrency.
 
-@param concurrency - Concurrency limit. Minimum: `1`.
+@param concurrency - Concurrency limit. Minimum: `1`. Can also be an options object.
 @returns A `limit` function.
 */
-export default function pLimit(concurrency: number): LimitFunction;
+export default function pLimit(concurrency: number | Options): LimitFunction;
 
 export type Options = {
 	/**

index.js

@@ -1,6 +1,10 @@
 import Queue from 'yocto-queue';
 
 export default function pLimit(concurrency) {
+	if (typeof concurrency === 'object') {
+		concurrency = concurrency.concurrency;
+	}
+
 	validateConcurrency(concurrency);
 
 	const queue = new Queue();

readme.md

@@ -36,11 +36,19 @@ Returns a `limit` function.
 
 #### concurrency
 
-Type: `number`\
+Type: `number | object`\
 Minimum: `1`
 
 Concurrency limit.
 
+You can pass a number or an options object with a `concurrency` property:
+
+```js
+import pLimit from 'p-limit';
+
+const limit = pLimit({concurrency: 1});
+```
+
 ### limit(fn, ...args)
 
 Returns the promise returned by calling `fn(...args)`.

test.js

@@ -208,6 +208,24 @@ test('map accepts an iterable (array iterator)', async t => {
 	t.deepEqual(results, [2, 4, 6, 8]);
 });
 
+test('accepts options object', async t => {
+	const limit = pLimit({concurrency: 1});
+
+	const input = [
+		limit(async () => {
+			await delay(50);
+			return 1;
+		}),
+		limit(async () => {
+			await delay(50);
+			return 2;
+		}),
+	];
+
+	t.deepEqual(await Promise.all(input), [1, 2]);
+	t.is(limit.concurrency, 1);
+});
+
 test('throws on invalid concurrency argument', t => {
 	t.throws(() => {
 		pLimit(0);
@@ -228,6 +246,14 @@ test('throws on invalid concurrency argument', t => {
 	t.throws(() => {
 		pLimit(true);
 	});
+
+	t.throws(() => {
+		pLimit({});
+	});
+
+	t.throws(() => {
+		pLimit({concurrency: 0});
+	});
 });
 
 test('change concurrency to smaller value', async t => {