feat(utils): add pick fn, improve omit

libs/util-fn/src/index.ts

@@ -12,6 +12,7 @@ export * from './kebab-case';
 export * from './deep-equal';
 export * from './extract-prefix-from-map-name';
 export * from './leaderboard-key';
+export * from './pick';
 export * from './omit';
 export * from './magic';
 export * from './approx-eq';

libs/util-fn/src/omit.spec.ts

@@ -13,6 +13,7 @@ describe('omit function', () => {
   });
 
   it('should return the same object if the key does not exist', () => {
+    // @ts-expect-error - testing invalid keys
     expect(omit({ a: 1, b: 2, c: 3 }, 'd')).toEqual({ a: 1, b: 2, c: 3 });
   });
 

libs/util-fn/src/omit.ts

@@ -1,18 +1,33 @@
-export function omit<T extends object>(
-  obj: T,
-  keys: string | string[]
-): Partial<T> {
-  const result = {};
-  for (const key of Object.keys(obj)) {
-    if (typeof keys === 'string') {
-      if (keys !== key) {
+export function omit<Obj extends object, Keys extends keyof Obj>(
+  obj: Obj,
+  keys: Keys
+): Omit<Obj, Keys>;
+
+export function omit<Obj extends object, Keys extends Array<keyof Obj>>(
+  obj: Obj,
+  keys: Keys
+): Omit<Obj, Keys[number]>;
+
+export function omit<
+  Obj extends object,
+  Keys extends keyof Obj | Array<keyof Obj>
+>(
+  obj: Obj,
+  keys: string | Array<keyof Obj>
+): Omit<Obj, Keys extends Array<keyof Obj> ? Keys[number] : Keys> {
+  const result: any = {};
+
+  for (const key of Object.keys(obj) as Array<keyof Obj>) {
+    if (Array.isArray(keys)) {
+      if (!keys.includes(key)) {
         result[key] = obj[key];
       }
     } else {
-      if (!keys.includes(key)) {
+      if (keys !== key) {
         result[key] = obj[key];
       }
     }
   }
+
   return result;
 }

libs/util-fn/src/pick.spec.ts

@@ -0,0 +1,56 @@
+import { pick } from './pick';
+
+describe('pick', () => {
+  it('returns an object with only the specified key when a single key is provided', () => {
+    const obj = { a: 1, b: 2, c: 3 };
+    const result = pick(obj, 'a');
+    expect(result).toEqual({ a: 1 });
+  });
+
+  it('returns an object with only the specified keys when an array of keys is provided', () => {
+    const obj = { a: 1, b: 2, c: 3 };
+    const result = pick(obj, ['a', 'c']);
+    expect(result).toEqual({ a: 1, c: 3 });
+  });
+
+  it('returns an empty object when none of the specified keys are present', () => {
+    const obj = { a: 1, b: 2, c: 3 };
+    // @ts-expect-error - intentionally testing non-existent keys
+    const result = pick(obj, ['d', 'e']);
+    expect(result).toEqual({});
+  });
+
+  it('returns an empty object when the input object is empty', () => {
+    const obj = {};
+    // @ts-expect-error - intentionally testing non-existent keys
+    const result = pick(obj, ['a', 'b']);
+    expect(result).toEqual({});
+  });
+
+  it('returns an empty object when the keys array is empty', () => {
+    const obj = { a: 1, b: 2, c: 3 };
+    const result = pick(obj, []);
+    expect(result).toEqual({});
+  });
+
+  it('returns an empty object when the key string is empty', () => {
+    const obj = { a: 1, b: 2, c: 3 };
+    // @ts-expect-error - intentionally testing non-existent keys
+    const result = pick(obj, '');
+    expect(result).toEqual({});
+  });
+
+  it('returns an object with only the specified key when the key is present multiple times', () => {
+    // @ts-expect-error - intentionally testing duplicate keys
+    const obj = { a: 1, b: 2, a: 3 };
+    const result = pick(obj, 'a');
+    expect(result).toEqual({ a: 3 });
+  });
+
+  it('returns an object with only the specified keys when the keys are present multiple times', () => {
+    // @ts-expect-error - intentionally testing duplicate keys
+    const obj = { a: 1, b: 2, a: 3, c: 4, c: 5 };
+    const result = pick(obj, ['a', 'c']);
+    expect(result).toEqual({ a: 3, c: 5 });
+  });
+});

libs/util-fn/src/pick.ts

@@ -0,0 +1,33 @@
+export function pick<Obj extends object, Keys extends keyof Obj>(
+  obj: Obj,
+  keys: Keys
+): Pick<Obj, Keys>;
+
+export function pick<Obj extends object, Keys extends Array<keyof Obj>>(
+  obj: Obj,
+  keys: Keys
+): Pick<Obj, Keys[number]>;
+
+export function pick<
+  Obj extends object,
+  Keys extends keyof Obj | Array<keyof Obj>
+>(
+  obj: Obj,
+  keys: Keys
+): Pick<Obj, Keys extends Array<keyof Obj> ? Keys[number] : Keys> {
+  const result: any = {};
+
+  for (const key of Object.keys(obj) as Array<keyof Obj>) {
+    if (Array.isArray(keys)) {
+      if (keys.includes(key)) {
+        result[key] = obj[key];
+      }
+    } else {
+      if (keys === key) {
+        result[key] = obj[key];
+      }
+    }
+  }
+
+  return result;
+}