Explain how the stack data structure works and what operations it supports.

A stack is a data structure that operates on the Last In, First Out (LIFO) principle, meaning the last added element is the first to be removed. Imagine a stack of plates: to take a plate, you remove the top one.

Main operations of a stack:

• push — add an element to the top of the stack;
• pop — remove and return the top element;
• peek (or top) — view the top element without removing it;
• isEmpty — check if the stack is empty.

Example in JavaScript (Node.js):

class Stack {
  constructor() {
    this.items = [];
  }

  push(element) {
    this.items.push(element);
  }

  pop() {
    if (this.isEmpty()) {
      return null;
    }
    return this.items.pop();
  }

  peek() {
    if (this.isEmpty()) {
      return null;
    }
    return this.items[this.items.length - 1];
  }

  isEmpty() {
    return this.items.length === 0;
  }
}

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

This demonstrates the basic stack operations.