Add TypeScript definition

index.d.ts

@@ -0,0 +1,55 @@
+declare namespace findUp {
+	interface Options {
+		/**
+		Directory to start from.
+
+		@default process.cwd()
+		*/
+		readonly cwd?: string;
+	}
+}
+
+declare const findUp: {
+	/**
+	Find a file or directory by walking up parent directories.
+
+	@param filename - Filename of the file or an array of files to find.
+	@returns Either the first filepath found (by respecting the order of `filename`s) or `null`.
+
+	@example
+	```
+	// /
+	// └── Users
+	// 		└── sindresorhus
+	// 				├── unicorn.png
+	// 				└── foo
+	// 						└── bar
+	// 								├── baz
+	// 								└── example.js
+
+	// example.js
+	import findUp = require('find-up');
+
+	(async () => {
+		console.log(await findUp('unicorn.png'));
+		//=> '/Users/sindresorhus/unicorn.png'
+
+		console.log(await findUp(['rainbow.png', 'unicorn.png']));
+		//=> '/Users/sindresorhus/unicorn.png'
+	})();
+	```
+	*/
+	(filename: string | string[], options?: findUp.Options): Promise<
+		string | null
+	>;
+
+	/**
+	Synchronously find a file or directory by walking up parent directories.
+
+	@param filename - Filename of the file or an array of files to find.
+	@returns Either the first filepath found (by respecting the order of `filename`s) or `null`.
+	*/
+	sync(filename: string | string[], options?: findUp.Options): string | null;
+};
+
+export = findUp;

index.js

@@ -2,45 +2,45 @@
 const path = require('path');
 const locatePath = require('locate-path');
 
-module.exports = (filename, opts = {}) => {
-	const startDir = path.resolve(opts.cwd || '');
-	const {root} = path.parse(startDir);
+module.exports = (filename, options = {}) => {
+	const startDirectory = path.resolve(options.cwd || '');
+	const {root} = path.parse(startDirectory);
 
 	const filenames = [].concat(filename);
 
 	return new Promise(resolve => {
-		(function find(dir) {
-			locatePath(filenames, {cwd: dir}).then(file => {
+		(function find(directory) {
+			locatePath(filenames, {cwd: directory}).then(file => {
 				if (file) {
-					resolve(path.join(dir, file));
-				} else if (dir === root) {
+					resolve(path.join(directory, file));
+				} else if (directory === root) {
 					resolve(null);
 				} else {
-					find(path.dirname(dir));
+					find(path.dirname(directory));
 				}
 			});
-		})(startDir);
+		})(startDirectory);
 	});
 };
 
-module.exports.sync = (filename, opts = {}) => {
-	let dir = path.resolve(opts.cwd || '');
-	const {root} = path.parse(dir);
+module.exports.sync = (filename, options = {}) => {
+	let directory = path.resolve(options.cwd || '');
+	const {root} = path.parse(directory);
 
 	const filenames = [].concat(filename);
 
 	// eslint-disable-next-line no-constant-condition
 	while (true) {
-		const file = locatePath.sync(filenames, {cwd: dir});
+		const file = locatePath.sync(filenames, {cwd: directory});
 
 		if (file) {
-			return path.join(dir, file);
+			return path.join(directory, file);
 		}
 
-		if (dir === root) {
+		if (directory === root) {
 			return null;
 		}
 
-		dir = path.dirname(dir);
+		directory = path.dirname(directory);
 	}
 };

index.test-d.ts

@@ -0,0 +1,16 @@
+import {expectType} from 'tsd';
+import findUp = require('.');
+
+expectType<Promise<string | null>>(findUp('unicorn.png'));
+expectType<Promise<string | null>>(findUp('unicorn.png', {cwd: ''}));
+expectType<Promise<string | null>>(findUp(['rainbow.png', 'unicorn.png']));
+expectType<Promise<string | null>>(
+	findUp(['rainbow.png', 'unicorn.png'], {cwd: ''})
+);
+
+expectType<string | null>(findUp.sync('unicorn.png'));
+expectType<string | null>(findUp.sync('unicorn.png', {cwd: ''}));
+expectType<string | null>(findUp.sync(['rainbow.png', 'unicorn.png']));
+expectType<string | null>(
+	findUp.sync(['rainbow.png', 'unicorn.png'], {cwd: ''})
+);

package.json

@@ -13,10 +13,11 @@
 		"node": ">=6"
 	},
 	"scripts": {
-		"test": "xo && ava"
+		"test": "xo && ava && tsd"
 	},
 	"files": [
-		"index.js"
+		"index.js",
+		"index.d.ts"
 	],
 	"keywords": [
 		"find",
@@ -43,8 +44,9 @@
 		"locate-path": "^3.0.0"
 	},
 	"devDependencies": {
-		"ava": "*",
+		"ava": "^1.4.1",
 		"tempy": "^0.2.1",
-		"xo": "*"
+		"tsd": "^0.7.2",
+		"xo": "^0.24.0"
 	}
 }