functionalStack.js

//stackUtils.js

export function peak(head){
  return head?.value
}

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

export function push(head){
  return (value) => {
     const node = {
      value,
      next : head
    }
    return node
  }
}

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

// index.js

import {push, pop, peak, getIterator} from './stackUtils.js'

let stack

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

stack = push(stack)(3)
stack = push(stack)(4)
stack = push(stack)(2)
let stackPusher = push(stack)

stack = stackPusher(2)

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