Require Node.js 8, add TypeScript definition (#11)

.travis.yml

@@ -2,4 +2,3 @@ language: node_js
 node_js:
   - '10'
   - '8'
-  - '6'

index.d.ts

@@ -0,0 +1,16 @@
+export interface Options {
+	/**
+	 * A dist-tag or a semver range.
+	 */
+	readonly version?: string;
+}
+
+/**
+ * Get the latest version of an npm package.
+ *
+ * @param name - The package name to look up the version for.
+ */
+export default function latestVersion(
+	name: string,
+	options?: Options
+): Promise<string>;

index.js

@@ -1,4 +1,11 @@
 'use strict';
+
 const packageJson = require('package-json');
 
-module.exports = (name, options) => packageJson(name.toLowerCase(), options).then(data => data.version);
+const lastestVersion = async (name, options) => {
+	const {version} = await packageJson(name.toLowerCase(), options);
+	return version;
+};
+
+module.exports = lastestVersion;
+module.exports.default = lastestVersion;

index.test-d.ts

@@ -0,0 +1,5 @@
+import {expectType} from 'tsd-check';
+import latestVersion from '.';
+
+expectType<Promise<string>>(latestVersion('ava'));
+expectType<Promise<string>>(latestVersion('npm', {version: 'latest-5'}));

package.json

@@ -10,13 +10,14 @@
 		"url": "sindresorhus.com"
 	},
 	"engines": {
-		"node": ">=6"
+		"node": ">=8"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd-check"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"latest",
@@ -29,12 +30,13 @@
 		"module"
 	],
 	"dependencies": {
-		"package-json": "^5.0.0"
+		"package-json": "^6.0.0"
 	},
 	"devDependencies": {
-		"ava": "*",
-		"semver": "^5.4.1",
+		"ava": "^1.3.1",
+		"semver": "^5.6.0",
 		"semver-regex": "^2.0.0",
-		"xo": "*"
+		"tsd-check": "^0.3.0",
+		"xo": "^0.24.0"
 	}
 }

test.js

@@ -1,20 +1,20 @@
 import test from 'ava';
 import semver from 'semver';
 import semverRegex from 'semver-regex';
-import m from '.';
+import latestVersion from '.';
 
 test('latest version', async t => {
-	t.regex(await m('ava'), semverRegex());
+	t.regex(await latestVersion('ava'), semverRegex());
 });
 
 test('latest version with version', async t => {
-	t.true(semver.satisfies(await m('package-json', {version: '0'}), '0.x'));
+	t.true(semver.satisfies(await latestVersion('package-json', {version: '0'}), '0.x'));
 });
 
 test('latest version with dist-tag', async t => {
-	t.true(semver.satisfies(await m('npm', {version: 'latest-5'}), '5.x'));
+	t.true(semver.satisfies(await latestVersion('npm', {version: 'latest-5'}), '5.x'));
 });
 
 test('latest version scoped', async t => {
-	t.regex(await m('@sindresorhus/df'), semverRegex());
+	t.regex(await latestVersion('@sindresorhus/df'), semverRegex());
 });