Add TypeScript definition

index.d.ts

@@ -0,0 +1,44 @@
+export type Reviver = (key: string, value: any) => any;
+export type BeforeParse = (data: string) => string;
+
+export interface Options {
+	/**
+	 * Applies a function to the JSON string before parsing.
+	 */
+	beforeParse?: BeforeParse;
+	/**
+	 * Prescribes how the value originally produced by parsing is transformed, before being returned.
+	 * See the [`JSON.parse` docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse#Using_the_reviver_parameter) for more.
+	 */
+	reviver?: Reviver;
+}
+
+/**
+ * Read and parse a JSON file.
+ *
+ * Strips UTF-8 BOM, uses graceful-fs, and throws more helpful JSON errors.
+ *
+ * @example
+ *
+ * import * as loadJsonFile from 'load-json-file';
+ *
+ * const json = loadJsonFile.sync('foo.json');
+ * //=> {foo: true}
+ */
+export function sync<T = any>(filePath: string, options?: Options): T;
+
+/**
+ * Read and parse a JSON file.
+ *
+ * Strips UTF-8 BOM, uses graceful-fs, and throws more helpful JSON errors.
+ *
+ * @example
+ *
+ * import loadJsonFile from 'load-json-file';
+ *
+ * (async () => {
+ * 	const json = await loadJsonFile('foo.json');
+ * 	//=> {foo: true}
+ * })();
+ */
+export default function loadJsonFile<T = any>(filePath: string, options?: Options): Promise<T>;

index.js

@@ -15,5 +15,8 @@ const parse = (data, filePath, options = {}) => {
 	return parseJson(data, options.reviver, path.relative(process.cwd(), filePath));
 };
 
-module.exports = (filePath, options) => pify(fs.readFile)(filePath, 'utf8').then(data => parse(data, filePath, options));
+const loadJsonFile = (filePath, options) => pify(fs.readFile)(filePath, 'utf8').then(data => parse(data, filePath, options));
+
+module.exports = loadJsonFile;
+module.exports.default = loadJsonFile;
 module.exports.sync = (filePath, options) => parse(fs.readFileSync(filePath, 'utf8'), filePath, options);

index.test-d.ts

@@ -0,0 +1,16 @@
+import {expectType} from 'tsd-check';
+import loadJsonFile, {sync, Reviver, BeforeParse} from '.';
+
+(async () => {
+	// To-Do => Expand Tests
+	// https://github.com/sindresorhus/write-json-file/blob/master/index.test-d.ts
+	expectType<Reviver>(() => 1);
+	expectType<Reviver>((a: string) => a.length);
+	expectType<Reviver>((a: string, b: string) => a.length - b.length);
+
+	expectType<BeforeParse>((data) => data);
+
+	expectType<void>(await loadJsonFile('unicorn.json'));
+
+	expectType<void>(sync('unicorn.json'));
+})();

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": [
 		"read",
@@ -35,6 +36,12 @@
 	},
 	"devDependencies": {
 		"ava": "*",
+		"tsd-check": "^0.1.0",
 		"xo": "*"
+	},
+	"xo": {
+		"ignores": [
+			"index.d.ts"
+		]
 	}
 }