Array Prototype Last

Problem Statement

In this task, we aim to modify the way arrays function in a specific way by allowing you to call a new method array.last() on any array, that would return the last element of that array. If the array is empty, the function should return -1. This enhancement should be versatile enough to handle any kind of arrays, particularly arrays derived from JSON data using JSON.parse. Extending the functionality of arrays in this manner allows for more intuitive handling and querying of data within standard programming workflows especially when dealing with API responses or any other form of structured data.

Examples

Example 1

Input:

nums = [null, {}, 3]

Output:

3

Explanation:

Calling nums.last() should return the last element: 3.

Example 2

Input:

nums = []

Output:

-1

Explanation:

Because there are no elements, return -1.

Constraints

• arr is a valid JSON array
• 0 <= arr.length <= 1000

Approach and Intuition

The key requirement is to augment the native Array prototype in a programming language such as JavaScript, since the array is derived from JSON.parse which produces a JavaScript array. We should a method .last() using JavaScript's prototype inheritance system.

1. The last() method:
   • Check if the array’s length is greater than 0. If yes, return the last element.
   • If the array is empty (length is 0), return -1.

Understanding Array Prototype Enhancement:

• By adding a method to Array.prototype, it ensures that all arrays inherit this method, similar to native functions like array.push() or array.pop().

Considered Constraints:

• The method must efficiently handle arrays with up to 1000 elements.
• It should consistently return the correct type of the last element whether it's null, an object, a number, etc., or -1 if the array is empty, which upholds the integrity of data types in JavaScript.

Here’s a sample enhancement step-wise:

1. Validate if the extending of the prototype might not clash with existing properties or future specifications.
2. Implement the enhancement with a simple conditional check for the array size. If the size is non-zero, extract and return the last element. Otherwise, default to -1.
3. Ensure performance impact is minimal by restricting the computation to simple property accesses and the length check.

By following these milestones, the .last() method on arrays can be easily interpreted and integrated, aligning with the JavaScript coding norms and expectations while ensuring functionality across diverse data types stored in arrays.

Solutions

Object.defineProperty(Array.prototype, 'getLast', {
  get: function() {
    return () => this.length ? this[this.length - 1] : undefined;
  }
});