Array Prototype Last

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.

Example 1:

Input: nums = [1,2,3]
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:

0 <= arr.length <= 1000
0 <= arr[i] <= 1000

解法:

這題是在講Array這個類別的擴展function，當呼叫last()的方法需要回傳最後一個的參數

declare global {
    interface Array<T> {
        last(): T | -1;
    }
}

Array.prototype.last = function() {

	// 找最後一個項目，找不到回傳-1
    const last = this.at(this.length - 1);
    return last ?? -1; 
};