refactor(packages/stdlib): stack return undefined on peek if it empty

packages/stdlib/src/structs/stack/index.test.ts

@@ -79,9 +79,11 @@ describe('stack', () => {
       expect(stack.length).toBe(3);
     });
 
-    it('throw an error if the stack is empty', () => {
+    it('return undefined if the stack is empty', () => {
       const stack = new Stack<number>();
-      expect(() => stack.peek()).toThrow(new RangeError('Stack is empty'));
+      const topElement = stack.peek();
+
+      expect(topElement).toBeUndefined();
     });
   });
 

packages/stdlib/src/structs/stack/index.ts

@@ -96,7 +96,7 @@ export class Stack<T> implements Iterable<T>, AsyncIterable<T> {
      */
     public peek() {
         if (this.isEmpty)
-            throw new RangeError('Stack is empty');
+            return undefined;
         
         return last(this.stack);
     }