fix: update ts solution to lc problem: No.2619 (doocs#1316)

2619.Array Prototype Last

Author: YangFong

solution/2600-2699/2619.Array Prototype Last/README.md

@@ -54,13 +54,15 @@ declare global {
 }
 
 Array.prototype.last = function () {
-    return this[this.length - 1] ?? -1;
+    return this.length ? this.at(-1) : -1;
 };
 
 /**
  * const arr = [1, 2, 3];
  * arr.last(); // 3
  */
+
+export {};
 ```
 
 ### **...**

solution/2600-2699/2619.Array Prototype Last/README_EN.md

@@ -46,13 +46,15 @@ declare global {
 }
 
 Array.prototype.last = function () {
-    return this[this.length - 1] ?? -1;
+    return this.length ? this.at(-1) : -1;
 };
 
 /**
  * const arr = [1, 2, 3];
  * arr.last(); // 3
  */
+
+export {};
 ```
 
 ### **...**

solution/2600-2699/2619.Array Prototype Last/Solution.ts

@@ -5,10 +5,12 @@ declare global {
 }
 
 Array.prototype.last = function () {
-    return this[this.length - 1] ?? -1;
+    return this.length ? this.at(-1) : -1;
 };
 
 /**
  * const arr = [1, 2, 3];
  * arr.last(); // 3
  */
+
+export {};