feat: add solutions to lc problems: No.2618~2621

* No.2618.Check if Object Instance of Class
* No.2619.Array Prototype Las
* No.2620.Counter
* No.2621.Sleep

Author: yanglbme

solution/2600-2699/2618.Check if Object Instance of Class/README.md

@@ -58,7 +58,23 @@ Dog 是 Animal 的子类。因此，Dog 对象同时是 Dog 和 Animal 的实例
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```ts
-
+function checkIfInstanceOf(obj: any, classFunction: any): boolean {
+    if (classFunction == null) {
+        return false;
+    }
+    while (obj != null) {
+        const proto = Object.getPrototypeOf(obj);
+        if (proto === classFunction.prototype) {
+            return true;
+        }
+        obj = proto;
+    }
+    return false;
+}
+
+/**
+ * checkIfInstanceOf(new Date(), Date); // true
+ */
 ```
 
 ### **...**

solution/2600-2699/2618.Check if Object Instance of Class/README_EN.md

@@ -52,7 +52,23 @@ Dog is a subclass of Animal. Therefore, a Dog object is an instance of both Dog
 ### **TypeScript**
 
 ```ts
-
+function checkIfInstanceOf(obj: any, classFunction: any): boolean {
+    if (classFunction == null) {
+        return false;
+    }
+    while (obj != null) {
+        const proto = Object.getPrototypeOf(obj);
+        if (proto === classFunction.prototype) {
+            return true;
+        }
+        obj = proto;
+    }
+    return false;
+}
+
+/**
+ * checkIfInstanceOf(new Date(), Date); // true
+ */
 ```
 
 ### **...**

solution/2600-2699/2618.Check if Object Instance of Class/Solution.ts

@@ -0,0 +1,17 @@
+function checkIfInstanceOf(obj: any, classFunction: any): boolean {
+    if (classFunction == null) {
+        return false;
+    }
+    while (obj != null) {
+        const proto = Object.getPrototypeOf(obj);
+        if (proto === classFunction.prototype) {
+            return true;
+        }
+        obj = proto;
+    }
+    return false;
+}
+
+/**
+ * checkIfInstanceOf(new Date(), Date); // true
+ */

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

@@ -46,7 +46,20 @@
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```ts
-
+declare global {
+    interface Array<T> {
+        last(): T | -1;
+    }
+}
+
+Array.prototype.last = function () {
+    return this[this.length - 1] ?? -1;
+};
+
+/**
+ * const arr = [1, 2, 3];
+ * arr.last(); // 3
+ */
 ```
 
 ### **...**

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

@@ -38,7 +38,20 @@ Write code that enhances all arrays such that you can call the&nbsp;<code>array.
 ### **TypeScript**
 
 ```ts
-
+declare global {
+    interface Array<T> {
+        last(): T | -1;
+    }
+}
+
+Array.prototype.last = function () {
+    return this[this.length - 1] ?? -1;
+};
+
+/**
+ * const arr = [1, 2, 3];
+ * arr.last(); // 3
+ */
 ```
 
 ### **...**

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

@@ -0,0 +1,14 @@
+declare global {
+    interface Array<T> {
+        last(): T | -1;
+    }
+}
+
+Array.prototype.last = function () {
+    return this[this.length - 1] ?? -1;
+};
+
+/**
+ * const arr = [1, 2, 3];
+ * arr.last(); // 3
+ */

solution/2600-2699/2620.Counter/README.md

@@ -53,7 +53,19 @@ n = -2
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```ts
-
+function createCounter(n: number): () => number {
+    let i = n;
+    return function () {
+        return i++;
+    };
+}
+
+/**
+ * const counter = createCounter(10)
+ * counter() // 10
+ * counter() // 11
+ * counter() // 12
+ */
 ```
 
 ### **...**

solution/2600-2699/2620.Counter/README_EN.md

@@ -45,7 +45,19 @@ n = -2
 ### **TypeScript**
 
 ```ts
-
+function createCounter(n: number): () => number {
+    let i = n;
+    return function () {
+        return i++;
+    };
+}
+
+/**
+ * const counter = createCounter(10)
+ * counter() // 10
+ * counter() // 11
+ * counter() // 12
+ */
 ```
 
 ### **...**

solution/2600-2699/2620.Counter/Solution.ts

@@ -0,0 +1,13 @@
+function createCounter(n: number): () => number {
+    let i = n;
+    return function () {
+        return i++;
+    };
+}
+
+/**
+ * const counter = createCounter(10)
+ * counter() // 10
+ * counter() // 11
+ * counter() // 12
+ */

solution/2600-2699/2621.Sleep/README.md

@@ -50,7 +50,14 @@ sleep(100).then(() => {
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```ts
-
+async function sleep(millis: number): Promise<void> {
+    return new Promise(r => setTimeout(r, millis));
+}
+
+/**
+ * let t = Date.now()
+ * sleep(100).then(() => console.log(Date.now() - t)) // 100
+ */
 ```
 
 ### **...**

solution/2600-2699/2621.Sleep/README_EN.md

@@ -41,7 +41,14 @@ sleep(100).then(() => {
 ### **TypeScript**
 
 ```ts
-
+async function sleep(millis: number): Promise<void> {
+    return new Promise(r => setTimeout(r, millis));
+}
+
+/**
+ * let t = Date.now()
+ * sleep(100).then(() => console.log(Date.now() - t)) // 100
+ */
 ```
 
 ### **...**

solution/2600-2699/2621.Sleep/Solution.ts

@@ -0,0 +1,8 @@
+async function sleep(millis: number): Promise<void> {
+    return new Promise(r => setTimeout(r, millis));
+}
+
+/**
+ * let t = Date.now()
+ * sleep(100).then(() => console.log(Date.now() - t)) // 100
+ */