feat: added isNullish()

Author: webdeveric

src/predicate/index.ts

@@ -26,6 +26,7 @@ export * from './isLengthAware.js';
 export * from './isNonNullable.js';
 export * from './isNull.js';
 export * from './isNullArray.js';
+export * from './isNullish.js';
 export * from './isNumber.js';
 export * from './isNumberArray.js';
 export * from './isNumericString.js';

src/predicate/isNullish.ts

@@ -0,0 +1 @@
+export const isNullish = (input: unknown): input is null | undefined => input == null;

test/predicate/isNullish.test.ts

@@ -0,0 +1,19 @@
+import { describe, it, expect } from 'vitest';
+
+import { isNullish } from '../../src/predicate/isNullish.js';
+
+describe('isNullish()', () => {
+  it('Returns true for valid input', () => {
+    expect(isNullish(undefined)).toBe(true);
+    expect(isNullish(null)).toBe(true);
+  });
+
+  it('Returns false for invalid input', () => {
+    expect(isNullish('abc123')).toBe(false);
+    expect(isNullish([])).toBe(false);
+  });
+
+  it('Can be used with Array.filter()', () => {
+    expect([1, null, 2, undefined, 3].filter(isNullish)).toEqual([null, undefined]);
+  });
+});