Add TypeScript definition (#27)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

index.d.ts

@@ -0,0 +1,18 @@
+export type Options = Readonly<{
+	/**
+	 * A preferred port or an array of preferred ports to use.
+	 */
+	port?: number | ReadonlyArray<number>,
+
+	/**
+	 * The host on which port resolution should be performed. Can be either an IPv4 or IPv6 address.
+	 */
+	host?: string;
+}>;
+
+/**
+ * Get an available port number.
+ *
+ * @returns Port number.
+ */
+export default function getPort(options?: Options): Promise<number>;

index.test-d.ts

@@ -0,0 +1,7 @@
+import {expectType} from 'tsd-check';
+import getPort from '.';
+
+expectType<number>(await getPort());
+expectType<number>(await getPort({port: 3000}));
+expectType<number>(await getPort({port: [3000, 3001, 3002]}));
+expectType<number>(await getPort({host: 'https://localhost'}));

package.json

@@ -13,10 +13,11 @@
 		"node": ">=6"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd-check"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"port",
@@ -38,6 +39,7 @@
 	"devDependencies": {
 		"ava": "*",
 		"pify": "^3.0.0",
+		"tsd-check": "^0.3.0",
 		"xo": "*"
 	}
 }