Add TypeScript definition (#21)

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

index.d.ts

@@ -0,0 +1,45 @@
+declare namespace internalIp {
+	/**
+	 * @returns The IPv6 address of the internet-facing interface, as determined from the default gateway. When the address cannot be determined for any reason, `null` will be returned.
+	 *
+	 * @example
+	 *
+	 * console.log(await internalIp.v6());
+	 * //=> 'fe80::1'
+	 */
+	export function v6(): Promise<string>;
+	export namespace v6 {
+		/**
+		 * @returns The IPv6 address of the internet-facing interface, as determined from the default gateway. When the address cannot be determined for any reason, `null` will be returned.
+		 *
+		 * @example
+		 *
+		 * console.log(internalIp.v6.sync());
+		 * //=> 'fe80::1'
+		 */
+		function sync(): string;
+	}
+
+	/**
+	 * @returns The IPv4 address of the internet-facing interface, as determined from the default gateway. When the address cannot be determined for any reason, `null` will be returned.
+	 *
+	 * @example
+	 *
+	 * console.log(await internalIp.v4())
+	 * //=> '10.0.0.79'
+	 */
+	export function v4(): Promise<string>;
+	export namespace v4 {
+		/**
+		 * @returns The IPv4 address of the internet-facing interface, as determined from the default gateway. When the address cannot be determined for any reason, `null` will be returned.
+		 *
+		 * @example
+		 *
+		 * console.log(internalIp.v4.sync())
+		 * //=> '10.0.0.79'
+		 */
+		function sync(): string;
+	}
+}
+
+export default internalIp;

index.js

@@ -40,8 +40,11 @@ function sync(family) {
 	}
 }
 
-module.exports.v6 = () => promise('v6');
-module.exports.v4 = () => promise('v4');
-
-module.exports.v6.sync = () => sync('v6');
-module.exports.v4.sync = () => sync('v4');
+const internalIp = {};
+internalIp.v6 = () => promise('v6');
+internalIp.v4 = () => promise('v4');
+internalIp.v6.sync = () => sync('v6');
+internalIp.v4.sync = () => sync('v4');
+
+module.exports = internalIp;
+module.exports.default = internalIp;

index.test-d.ts

@@ -0,0 +1,8 @@
+import {expectType} from 'tsd-check';
+import internalIp from '.';
+
+expectType<string>(await internalIp.v4());
+expectType<string>(await internalIp.v6());
+
+expectType<string>(internalIp.v4.sync());
+expectType<string>(internalIp.v6.sync());

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": [
 		"ip",
@@ -36,6 +37,7 @@
 	},
 	"devDependencies": {
 		"ava": "^1.2.1",
+		"tsd-check": "^0.3.0",
 		"xo": "^0.24.0"
 	}
 }