Add TypeScript definition (#20)

index.d.ts

@@ -0,0 +1,24 @@
+export interface Options {
+	/**
+	 * Use a key distance-based score to leniently accept typos of `yes` and `no`.
+	 *
+	 * @default false
+	 */
+	lenient?: boolean;
+
+	/**
+	 * Default value if no match was found.
+	 *
+	 * @default null
+	 */
+	default?: boolean | null;
+}
+
+/**
+ * Parse yes/no like values.
+ * The following case-insensitive values are recognized: `'y', 'yes', 'true', true, '1', 1, 'n', 'no', 'false', false, '0', 0`
+ *
+ * @param input - Value that should be converted.
+ * @returns The parsed input if it can be parsed or the default value defined in the `default` option.
+ */
+export default function yn(input: any, options?: Options): boolean | null;

index.js

@@ -26,3 +26,5 @@ module.exports = (val, opts) => {
 
 	return opts.default;
 };
+
+module.exports.default = module.exports;

index.test-d.ts

@@ -0,0 +1,11 @@
+import {expectType} from 'tsd-check';
+import yn from '.';
+
+// Should use null as default when no options are given
+expectType<boolean | null>(yn('true'));
+
+// Should use the default type when given
+expectType<boolean | null>(yn('true', {default: null}));
+
+// Should use null as default when only the lenient option is given
+expectType<boolean | null>(yn('true', {lenient: true}));

package.json

@@ -17,11 +17,12 @@
     "node": ">=4"
   },
   "scripts": {
-    "test": "xo && ava"
+    "test": "xo && ava && tsd-check"
   },
   "files": [
     "index.js",
-    "lenient.js"
+    "lenient.js",
+    "index.d.ts"
   ],
   "keywords": [
     "yn",
@@ -39,6 +40,7 @@
   ],
   "devDependencies": {
     "ava": "*",
+    "tsd-check": "*",
     "xo": "*"
   }
 }