From b1cd76b93bc525e77527da6a07b458183febd43b Mon Sep 17 00:00:00 2001
From: Sindre Sorhus <sindresorhus@gmail.com>
Date: Sun, 1 Dec 2019 16:12:38 +0700
Subject: [PATCH] Return `undefined` instead of `null` when no match

---
 index.d.ts      |  8 ++++----
 index.js        |  4 ++--
 index.test-d.ts |  4 ++--
 readme.md       |  6 +++---
 test.js         | 22 +++++++++++-----------
 5 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/index.d.ts b/index.d.ts
index 630313c..6e1a5b4 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -10,9 +10,9 @@ declare namespace yn {
 		/**
 		Default value if no match was found.
 
-		@default null
+		@default undefined
 		*/
-		readonly default?: boolean | null;
+		readonly default?: boolean | undefined;
 	}
 
 	interface OptionsWithDefault extends Options {
@@ -42,7 +42,7 @@ yn(true);
 //=> true
 
 yn('abomasum');
-//=> null
+//=> undefined
 
 yn('abomasum', {default: false});
 //=> false
@@ -52,6 +52,6 @@ yn('mo', {lenient: true});
 ```
 */
 declare function yn(input: unknown, options: yn.OptionsWithDefault): boolean;
-declare function yn(input: unknown, options?: yn.Options): boolean | null;
+declare function yn(input: unknown, options?: yn.Options): boolean | undefined;
 
 export = yn;
diff --git a/index.js b/index.js
index 6f61522..daef73b 100644
--- a/index.js
+++ b/index.js
@@ -3,11 +3,11 @@ const lenientFunction = require('./lenient');
 
 const yn = (value, {
 	lenient = false,
-	default: default_ = null
+	default: default_
 } = {}) => {
 	value = String(value).trim();
 
-	if (default_ !== null && typeof default_ !== 'boolean') {
+	if (default_ !== undefined && typeof default_ !== 'boolean') {
 		throw new TypeError(`Expected the \`default\` option to be of type \`boolean\`, got \`${typeof default_}\``);
 	}
 
diff --git a/index.test-d.ts b/index.test-d.ts
index 220701d..92ce6d5 100644
--- a/index.test-d.ts
+++ b/index.test-d.ts
@@ -1,6 +1,6 @@
 import {expectType} from 'tsd';
 import yn = require('.');
 
-expectType<boolean | null>(yn('y'));
-expectType<boolean | null>(yn('mo', {lenient: true}));
+expectType<boolean | undefined>(yn('y'));
+expectType<boolean | undefined>(yn('mo', {lenient: true}));
 expectType<boolean>(yn('abomasum', {default: false}));
diff --git a/readme.md b/readme.md
index 1a66017..ccdfaf6 100644
--- a/readme.md
+++ b/readme.md
@@ -37,7 +37,7 @@ yn(true);
 //=> true
 
 yn('abomasum');
-//=> null
+//=> undefined
 
 yn('abomasum', {default: false});
 //=> false
@@ -46,7 +46,7 @@ yn('mo', {lenient: true});
 //=> false
 ```
 
-Unrecognized values return `null`.
+Unrecognized values return `undefined`.
 
 
 ## API
@@ -73,6 +73,6 @@ Use a key distance-based score to leniently accept typos of `yes` and `no`.
 ##### default
 
 Type: `boolean`\
-Default: `null`
+Default: `undefined`
 
 Default value if no match was found.
diff --git a/test.js b/test.js
index 3f95d2d..44367ef 100644
--- a/test.js
+++ b/test.js
@@ -15,9 +15,9 @@ const truthyCases = [
 	1
 ];
 test('truthy cases', t => {
-	for (const truthyCase of truthyCases) {
-		t.true(yn(truthyCase));
-		t.true(yn(truthyCase, {lenient: true}));
+	for (const case_ of truthyCases) {
+		t.true(yn(case_));
+		t.true(yn(case_, {lenient: true}));
 	}
 });
 
@@ -35,13 +35,13 @@ const falseyCases = [
 	0
 ];
 test('falsey cases', t => {
-	for (const falseyCase of falseyCases) {
-		t.false(yn(falseyCase));
-		t.false(yn(falseyCase, {lenient: true}));
+	for (const case_ of falseyCases) {
+		t.false(yn(case_));
+		t.false(yn(case_, {lenient: true}));
 	}
 });
 
-const nullCases = [
+const undefinedCases = [
 	// Falsey cases that don't work
 	NaN,
 	null,
@@ -66,10 +66,10 @@ const nullCases = [
 	// Other
 	'unicorn'
 ];
-test('null cases', t => {
-	for (const nullCase of nullCases) {
-		t.is(yn(nullCase), null);
-		t.is(yn(nullCase, {lenient: true}), null);
+test('undefined cases', t => {
+	for (const case_ of undefinedCases) {
+		t.is(yn(case_), undefined);
+		t.is(yn(case_, {lenient: true}), undefined);
 	}
 });