Algorithm
30 Days of JavaScript
Array Prototype Last

2619. Array Prototype Last

Tags

  • JSON

Link

https://leetcode.com/problems/array-prototype-last/description/?envType=study-plan-v2&envId=30-days-of-javascript (opens in a new tab)

Question

Write code that enhances all arrays such that you can call the array.last() method on any array and it will return the last element. If there are no elements in the array, it should return -1.

You may assume the array is the output of JSON.parse.

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

Answer

JavaScript

/**
 * @return {null|boolean|number|string|Array|Object}
 */
Array.prototype.last = function () {
  if (this.length === 0) {
    return -1;
  }
  return this[this.length - 1];
 
  // return this.length === 0 ? -1 : this[this.length - 1]
};
 
/**
 * const arr = [1, 2, 3];
 * arr.last(); // 3
 */
Apply Transform over Each Element in ArrayArray Reduce Transformation