#91 Stack

Implement a stack data structure in JavaScript. A stack is a collection that follows the Last-In-First-Out (LIFO) principle. Your stack should have the following methods:

• push(element): Adds an element to the top of the stack.
• pop(): Removes the top element from the stack and returns it. Returns undefined if the stack is empty.
• peek(): Returns the top element of the stack without removing it. Returns undefined if the stack is empty.
• isEmpty(): Returns true if the stack is empty, otherwise returns false.
• size(): Returns the number of elements in the stack.

Use the following example to understand how the stack should work:

class Stack {
  // Your implementation here

}

const stack = new Stack();
stack.push(1);
stack.push(2);
console.log(stack.peek()); // 2

console.log(stack.pop());  // 2

console.log(stack.size()); // 1

console.log(stack.isEmpty()); // false

stack.pop();
console.log(stack.isEmpty()); // true