test: 2619

Author: shahadathhs

src/__tests__/2619-array-prototype-last.test.ts

@@ -0,0 +1,38 @@
+import '@/app/2619-array-prototype-last';
+
+describe('Problem 2619: Array.prototype.last', () => {
+  test('last returns last element for non-empty arrays', () => {
+    expect([1, 2, 3].last()).toBe(3);
+    expect(['a', 'b', 'c'].last()).toBe('c');
+    expect([true, false].last()).toBe(false);
+  });
+
+  test('last returns -1 for empty arrays', () => {
+    expect([].last()).toBe(-1);
+    expect(([] as number[]).last()).toBe(-1);
+  });
+
+  test('last works after array mutations', () => {
+    const arr = [10, 20];
+    expect(arr.last()).toBe(20);
+    arr.push(30);
+    expect(arr.last()).toBe(30);
+    arr.pop();
+    expect(arr.last()).toBe(20);
+    arr.splice(0, arr.length);
+    expect(arr.last()).toBe(-1);
+  });
+
+  test('last does not modify the array', () => {
+    const arr = [5, 6, 7];
+    const before = [...arr];
+    arr.last();
+    expect(arr).toEqual(before);
+  });
+
+  test('last is available on all array instances', () => {
+    class MyArray extends Array<number> {}
+    const myArr = new MyArray(1, 2, 3);
+    expect(myArr.last()).toBe(3);
+  });
+});

src/app/2619-array-prototype-last.ts

@@ -27,6 +27,7 @@
 //   https://leetcode.com/problems/array-prototype-last/description
 
 // * Solution
+// eslint-disable-next-line @typescript-eslint/no-unused-vars
 interface Array<T> {
   last(): T | -1;
 }
@@ -36,7 +37,7 @@ Array.prototype.last = function () {
 };
 
 // * Usage
-const arr: Array<number> = [1, 2, 3];
+// const arr: Array<number> = [1, 2, 3];
 
-console.log(arr.last()); // 3
-console.log(arr.last()); // -1
+// console.log(arr.last()); // 3
+// console.log(arr.last()); // -1