feat: add deepFreeze function and corresponding tests for object immutability

Author: tomast1337

shared/validation/common/deepFreeze.spec.ts

@@ -0,0 +1,69 @@
+import { deepFreeze } from './deepFreeze';
+
+describe('deepFreeze', () => {
+  it('should deeply freeze an object', () => {
+    const obj = {
+      a: 1,
+      b: {
+        c: 2,
+        d: {
+          e: 3,
+        },
+      },
+    };
+
+    const frozenObj = deepFreeze(obj);
+
+    expect(Object.isFrozen(frozenObj)).toBe(true);
+    expect(Object.isFrozen(frozenObj.b)).toBe(true);
+    expect(Object.isFrozen(frozenObj.b.d)).toBe(true);
+  });
+
+  it('should not allow modification of a deeply frozen object', () => {
+    const obj = {
+      a: 1,
+      b: {
+        c: 2,
+        d: {
+          e: 3,
+        },
+      },
+    };
+
+    const frozenObj = deepFreeze(obj);
+
+    expect(() => {
+      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+      // @ts-ignore
+      frozenObj.a = 2;
+    }).toThrow(TypeError);
+
+    expect(() => {
+      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+      // @ts-ignore
+      frozenObj.b.c = 3;
+    }).toThrow(TypeError);
+
+    expect(() => {
+      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+      // @ts-ignore
+      frozenObj.b.d.e = 4;
+    }).toThrow(TypeError);
+  });
+
+  it('should return the same object reference', () => {
+    const obj = {
+      a: 1,
+      b: {
+        c: 2,
+        d: {
+          e: 3,
+        },
+      },
+    };
+
+    const frozenObj = deepFreeze(obj);
+
+    expect(frozenObj).toBe(obj);
+  });
+});

shared/validation/common/deepFreeze.ts

@@ -1,6 +1,6 @@
-export function deepFreeze<T extends { [key: string]: any }>(
+export const deepFreeze = <T extends { [key: string]: any }>(
   object: T,
-): Readonly<T> {
+): Readonly<T> => {
   const propNames = Object.getOwnPropertyNames(object);
 
   for (const name of propNames) {
@@ -13,4 +13,4 @@ export function deepFreeze<T extends { [key: string]: any }>(
   }
 
   return Object.freeze(object);
-}
+};