Stack.js

class Stack {
  #head;
 
  push(value){
    const node = {
      value,
      next : this.#head
    }
   
    this.#head = node
  }
  peak(){
    return this.#head?.value
  }
  pop(){
    const safeNode = this.#head ?? {}
    const poppedValue = safeNode.value;
    this.#head = safeNode.next;
    return poppedValue;
  }

  [Symbol.iterator]=function*(){
    let safeNode = this.#head ?? {}
    while(safeNode.value){
      yield safeNode.value
      safeNode = safeNode.next ?? {}
    }
  }
}

const stack = new Stack()

stack.push(1)
stack.push(2)
stack.peak() // 2
stack.pop() // 2
stack.peak() // 1

stack.push(3)
stack.push(4)
stack.push(2)
stack.push(2)

console.log([...stack]) // [ 2, 2, 4, 3, 1 ]