Creating a stack type in JS

stack.js

class Stack {
  constructor() {
    this._size = 0
    this._storage = {}
  }
  getSize() {
    return this._size
  }
  getStorage() {
    return this._storage
  }
  push(data) {
    const size = ++this._size
    this._storage[size] = data
  }
 pop() {
    const size = this._size
    let deletedData
 
    if (size) {
        deletedData = this._storage[size]
 
        delete this._storage[size]
        this._size--
 
        return deletedData
    }
 }
}

Inspired by https://code.tutsplus.com/series/data-structures-in-javascript--cms-772