feat(isUndefined): Add compatibility with lodash

benchmarks/performance/isUndefined.bench.ts

@@ -0,0 +1,18 @@
+import { bench, describe } from 'vitest';
+import { isUndefined as isUndefinedToolkit } from 'es-toolkit';
+import { isUndefined as isUndefinedLodash } from 'lodash';
+
+describe('isUndefined', () => {
+  bench('es-toolkit/isUndefined', () => {
+    isUndefinedToolkit(undefined);
+    isUndefinedToolkit(null);
+    isUndefinedToolkit('');
+    isUndefinedToolkit(123);
+  });
+  bench('lodash/isUndefined', () => {
+    isUndefinedLodash(undefined);
+    isUndefinedLodash(null);
+    isUndefinedLodash('');
+    isUndefinedLodash(123);
+  });
+});

docs/compatibility.md

@@ -228,7 +228,7 @@ Even if a feature is marked "in review," it might already be under review to ens
 | [isString](https://lodash.com/docs/4.17.15#isString)                   | ❌                    |
 | [isSymbol](https://lodash.com/docs/4.17.15#isSymbol)                   | ❌                    |
 | [isTypedArray](https://lodash.com/docs/4.17.15#isTypedArray)           | ❌                    |
-| [isUndefined](https://lodash.com/docs/4.17.15#isUndefined)             | 📝                    |
+| [isUndefined](https://lodash.com/docs/4.17.15#isUndefined)             | ✅                    |
 | [isWeakMap](https://lodash.com/docs/4.17.15#isWeakMap)                 | ❌                    |
 | [isWeakSet](https://lodash.com/docs/4.17.15#isWeakSet)                 | ❌                    |
 | [lt](https://lodash.com/docs/4.17.15#lt)                               | ❌                    |

docs/ko/compatibility.md

@@ -229,7 +229,7 @@ chunk([1, 2, 3, 4], 0);
 | [isString](https://lodash.com/docs/4.17.15#isString)                   | ❌        |
 | [isSymbol](https://lodash.com/docs/4.17.15#isSymbol)                   | ❌        |
 | [isTypedArray](https://lodash.com/docs/4.17.15#isTypedArray)           | ❌        |
-| [isUndefined](https://lodash.com/docs/4.17.15#isUndefined)             | 📝        |
+| [isUndefined](https://lodash.com/docs/4.17.15#isUndefined)             | ✅        |
 | [isWeakMap](https://lodash.com/docs/4.17.15#isWeakMap)                 | ❌        |
 | [isWeakSet](https://lodash.com/docs/4.17.15#isWeakSet)                 | ❌        |
 | [lt](https://lodash.com/docs/4.17.15#lt)                               | ❌        |

docs/zh_hans/compatibility.md

@@ -228,7 +228,7 @@ chunk([1, 2, 3, 4], 0);
 | [isString](https://lodash.com/docs/4.17.15#isString)                   | ❌       |
 | [isSymbol](https://lodash.com/docs/4.17.15#isSymbol)                   | ❌       |
 | [isTypedArray](https://lodash.com/docs/4.17.15#isTypedArray)           | ❌       |
-| [isUndefined](https://lodash.com/docs/4.17.15#isUndefined)             | 📝       |
+| [isUndefined](https://lodash.com/docs/4.17.15#isUndefined)             | ✅       |
 | [isWeakMap](https://lodash.com/docs/4.17.15#isWeakMap)                 | ❌       |
 | [isWeakSet](https://lodash.com/docs/4.17.15#isWeakSet)                 | ❌       |
 | [lt](https://lodash.com/docs/4.17.15#lt)                               | ❌       |

src/compat/predicate/isUndefined.spec.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it } from 'vitest';
+import { isUndefined } from '../../predicate';
+import { falsey } from '../_internal/falsey';
+
+describe('isUndefined', () => {
+  it('should return `true` for `undefined` values', () => {
+    expect(isUndefined(undefined)).toBe(true);
+  });
+
+  it('should return `false` for non `undefined` values', () => {
+    const expected = falsey.map(value => value === undefined);
+    const actual = falsey.map((value, index) => (index ? isUndefined(value) : isUndefined(undefined)));
+    expect(actual).toEqual(expected);
+
+    (function (..._: any[]) {
+      // eslint-disable-next-line prefer-rest-params
+      expect(isUndefined(arguments)).toBe(false);
+    })(1, 2, 3);
+    expect(isUndefined([1, 2, 3])).toBe(false);
+    expect(isUndefined(true)).toBe(false);
+    expect(isUndefined(new Date())).toBe(false);
+    expect(isUndefined(new Error())).toBe(false);
+    expect(isUndefined(Array.prototype.slice)).toBe(false);
+    expect(isUndefined({ a: 1 })).toBe(false);
+    expect(isUndefined(1)).toBe(false);
+    expect(isUndefined(/x/)).toBe(false);
+    expect(isUndefined('a')).toBe(false);
+    expect(isUndefined(Symbol('a'))).toBe(false);
+  });
+});