Understanding Stacks in JavaScript

Hey friends 👋

It’s another Tutorial Wednesday, and today we’re learning about one of the simplest data structures: Stacks.

Think of a stack like a pile of plates 🍽️:

• You add a plate on top → push()
• You remove the top plate → pop()
• You just want to see the top plate → peek()

This system is called LIFO (Last In, First Out). The last item you put in is the first one to come out.

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Implementing a Stack in JavaScript

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

  // Add item
  push(element) {
    this.items.push(element);
  }

  // Remove top item
  pop() {
    return this.items.pop();
  }

  // See top item
  peek() {
    return this.items[this.items.length - 1];
  }

  // Check if empty
  isEmpty() {
    return this.items.length === 0;
  }

  // Size of stack
  size() {
    return this.items.length;
  }
}

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

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Try It Yourself

Here’s a live playground where you can push, pop and peek items in a stack:

👉 Play with the Stack on CodePen

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Real-World Uses of Stacks

• Undo/Redo in text editors
• Browser history (back/forward buttons)
• Function call stack in JavaScript

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🙋🏽‍♀️ Over to You!

Try expanding this stack:

• Add a Clear Stack button
• Show the entire stack visually as a vertical list
• Limit stack size (like a plate rack with max capacity)

Next Wednesday, we’ll explore Queues — the opposite of stacks, FIFO (First In, First Out). Stay tuned!

Let me know if you do the challenge! I'd like to see yours! Connect with me on GitHub

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