스택 그리고 큐

Stack

class Stack {
  constructor() {
    this.items = [];
  }
  push(item) {
    this.items.push(item);
  }
  pop() {
    if (this.isEmpty()) {
      return null;
    } else {
      return this.items.pop();
    }
  }
  isEmpty() {
    return this.items.length === 0;
  }
  size() {
    return this.items.length;
  }
}
const myStack = new Stack();
myStack.push(1);
myStack.push(2);
myStack.push(3);
console.log(myStack.pop()); // Output: 3
console.log(myStack.pop()); // Output: 2
console.log(myStack.pop()); // Output: 1
console.log(myStack.pop()); // Output: null

Queue

class Queue {
  constructor() {
    this.items = [];
  }
  enqueue(item) {
    this.items.push(item);
  }
  dequeue() {
    if (this.isEmpty()) {
      return null;
    } else {
      return this.items.shift();
    }
  }
  isEmpty() {
    return this.items.length === 0;
  }
  size() {
    return this.items.length;
  }
}

// Example usage of the queue
const myQueue = new Queue();
myQueue.enqueue(1);
myQueue.enqueue(2);
myQueue.enqueue(3);
console.log(myQueue.dequeue()); // Output: 1
console.log(myQueue.dequeue()); // Output: 2
console.log(myQueue.dequeue()); // Output: 3
console.log(myQueue.dequeue()); // Output: null