class Stack { constructor() { this.data = []; } peek() { if(this.data.length === 0) return ''; return this.data[this.data.length-1]; } pop() { if(this.data.length === 0) return; return this.data.pop() } push(value) { this.data.push(value); return this } } const stack = new Stack(); stack.push('mail.ru'); // 1 stack.push('yandex.ru'); // 2 stack.push('wb.ru'); // 3 console.log(stack.peek()); stack.pop(); stack.pop(); stack.pop(); console.log(stack.peek());