Add use-singleton hook

package.json

@@ -3,13 +3,7 @@
   "version": "0.0.6",
   "description": "A collection of reusable react hooks for state and UI management",
   "homepage": "https://github.com/codiume/hooks.git",
-  "keywords": [
-    "hooks",
-    "library",
-    "react",
-    "react-hooks",
-    "state"
-  ],
+  "keywords": ["hooks", "library", "react", "react-hooks", "state"],
   "author": "MHD <[email protected]>",
   "contributors": [
     {
@@ -21,9 +15,7 @@
   "main": "./dist/index.cjs",
   "module": "./dist/index.js",
   "types": "./dist/index.d.ts",
-  "files": [
-    "dist"
-  ],
+  "files": ["dist"],
   "exports": {
     ".": {
       "import": {

src/index.ts

@@ -1,2 +1,3 @@
 export { useQueue } from './use-queue/use-queue';
 export { useScroll } from './use-scroll/use-scroll';
+export { useSingleton } from './use-singleton/use-singleton';

src/use-singleton/use-singleton.test.ts

@@ -0,0 +1,32 @@
+import { renderHook } from '@testing-library/react';
+import { describe, expect, it, vi } from 'vitest';
+import { useSingleton } from './use-singleton';
+
+describe('useSingleton', () => {
+  it('should call the initializer function only once', () => {
+    const initializer = vi.fn(() => ({ value: 'singleton' }));
+
+    const { rerender } = renderHook(() => useSingleton(initializer));
+
+    expect(initializer).toHaveBeenCalledTimes(1);
+
+    rerender();
+    rerender();
+
+    expect(initializer).toHaveBeenCalledTimes(1);
+  });
+
+  it('should return the same instance on re-renders', () => {
+    const initializer = () => ({ value: Math.random() });
+
+    const { result, rerender } = renderHook(() => useSingleton(initializer));
+
+    const firstInstance = result.current;
+
+    rerender();
+
+    const secondInstance = result.current;
+
+    expect(firstInstance).toBe(secondInstance);
+  });
+});

src/use-singleton/use-singleton.ts

@@ -0,0 +1,15 @@
+import { useRef } from 'react';
+
+/**
+ * React hook for creating a singleton value.
+ * @see https://github.com/Andarist/use-constant
+ */
+export function useSingleton<ValueType>(fn: () => ValueType): ValueType {
+  const ref = useRef<{ value: ValueType }>();
+
+  if (!ref.current) {
+    ref.current = { value: fn() };
+  }
+
+  return ref.current.value;
+}