stackUtils.js

const stackUtils = {
  push(head, value){
    const node = {
      value,
      next : head
    }
   
    return node
  },

  peak(head){
    return head?.value
  },

  pop(head){
    const safeNode = head ?? {}
  
    return safeNode.next;
  },

  getIterator(head){
    return (function*(){
    let safeNode = head ?? {}
      while(safeNode.value){
        yield safeNode.value
        safeNode = safeNode.next ?? {}
      }
    })()
  }
}

let stack

stack = stackUtils.push(stack, 1)
stack = stackUtils.push(stack, 2)
stackUtils.peak(stack) // 2
stack = stackUtils.pop(stack)
stackUtils.peak(stack) // 1

stack = stackUtils.push(stack, 3)
stack = stackUtils.push(stack, 4)
stack = stackUtils.push(stack, 2)
stack = stackUtils.push(stack, 2)

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