Require Node.js 8, add TypeScript definition, update dependencies (#3)

.gitattributes

@@ -1,2 +1 @@
-* text=auto
-*.js text eol=lf
+* text=auto eol=lf

.travis.yml

@@ -1,5 +1,4 @@
 language: node_js
 node_js:
+  - '10'
   - '8'
-  - '6'
-  - '4'

index.d.ts

@@ -0,0 +1,9 @@
+/**
+ * Run promise-returning & async functions in series.
+ *
+ * @param tasks - Functions are expected to return a value. If a Promise is returned, it's awaited before continuing with the next task.
+ * @returns A `Promise` that is fulfilled when all promises returned from calling the functions in `tasks` are fulfilled, or rejects if any of the promises reject. The fulfilled value is an `Array` of the fulfilled values.
+ */
+export default function pSeries<ValueType>(
+	tasks: Iterable<() => Promise<ValueType> | ValueType>
+): Promise<ValueType[]>;

index.js

@@ -1,21 +1,26 @@
 'use strict';
+
 const pReduce = require('p-reduce');
 const is = require('@sindresorhus/is');
 
-module.exports = iterable => {
-	const ret = [];
+const pSeries = async tasks => {
+	const results = [];
 
-	for (const task of iterable) {
+	for (const task of tasks) {
 		const type = is(task);
 
 		if (type !== 'Function') {
-			return Promise.reject(new TypeError(`Expected task to be a \`Function\`, received \`${type}\``));
+			throw new TypeError(`Expected task to be a \`Function\`, received \`${type}\``);
 		}
 	}
 
-	return pReduce(iterable, (_, fn) => {
-		return Promise.resolve().then(fn).then(val => {
-			ret.push(val);
-		});
-	}).then(() => ret);
+	await pReduce(tasks, async (_, task) => {
+		const value = await task();
+		results.push(value);
+	});
+
+	return results;
 };
+
+module.exports = pSeries;
+module.exports.default = pSeries;

index.test-d.ts

@@ -0,0 +1,9 @@
+import {expectType} from 'tsd-check';
+import pSeries from '.';
+
+expectType<Promise<(number | boolean)[]>>(
+	pSeries<number | boolean>([() => Promise.resolve(1), () => true])
+);
+expectType<Promise<(number | boolean)[]>>(
+	pSeries<number | boolean>(new Set([() => Promise.resolve(1), () => true]))
+);

package.json

@@ -10,13 +10,14 @@
 		"url": "sindresorhus.com"
 	},
 	"engines": {
-		"node": ">=4"
+		"node": ">=8"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd-check"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"promise",
@@ -37,11 +38,12 @@
 		"bluebird"
 	],
 	"dependencies": {
-		"@sindresorhus/is": "^0.7.0",
+		"@sindresorhus/is": "^0.15.0",
 		"p-reduce": "^1.0.0"
 	},
 	"devDependencies": {
-		"ava": "*",
-		"xo": "*"
+		"ava": "^1.3.1",
+		"tsd-check": "^0.3.0",
+		"xo": "^0.24.0"
 	}
 }

test.js

@@ -1,21 +1,20 @@
 import test from 'ava';
-import m from '.';
+import pSeries from '.';
 
-test(async t => {
+test('pSeries', async t => {
 	const input = [
 		async () => 1 + 1,
 		() => 2 + 2,
 		async () => 3 + 3
 	];
 
-	t.deepEqual(await m(input), [2, 4, 6]);
+	t.deepEqual(await pSeries(input), [2, 4, 6]);
 
-	const fixtureErr = new Error('fixture');
-	await t.throws(m([async () => Promise.reject(fixtureErr)]), fixtureErr.message);
+	const fixtureError = new Error('fixture');
+	await t.throwsAsync(pSeries([async () => Promise.reject(fixtureError)]), fixtureError.message);
 });
 
 test('throw if input is not a function', async t => {
 	const input = [Promise.resolve(1 + 1)];
-	const type = /^v4\./.test(process.version) ? 'Object' : 'Promise';
-	await t.throws(m(input), `Expected task to be a \`Function\`, received \`${type}\``);
+	await t.throwsAsync(pSeries(input), 'Expected task to be a `Function`, received `Promise`');
 });