My attemp to recall a simple stack implementation in JavaScipt

stack.js

/**
From: A Gentle Introduction to Data Structures: How Stacks Work
By: Michael Olorunnisola
https://medium.freecodecamp.com/data-structures-stacks-on-stacks-c25f2633c529
**/

class Stack {
	/**
	the underscore before the variable names signifies to other developers these variables are private,
	and shouldn’t be manipulated externally, only by the methods on the class
	**/
	constructor() {
		this._storage = {};
		this._position = -1;
	}
	
	/**
	to return the current position of the stack
	**/
	top() {
		return this._position();
	}
	
	/**
	add item to the stack
	**/
	push(value) {
		this._position++;
		this._storage[this._position] = value;
	}
	
	/**
	remove item from the stack
	**/
	pop(){
		// Check if the stack is not empty
		if(this._position > -1){
			let val = this._storage[this._position];
			delete this._storage[this._position];
			this._position--;
			return val;
		}
	}
}

// Make a browser history stack
let browserHistory = new Stack();
// Make a stack to save deleted history so we can access it again later (Forward Button)
let forward = new Stack();

// Insert value to stack (We accessed these sites in order)
browserHistory.push("www.google.com"); // Navigating to google
browserHistory.push("www.facebook.com"); // Navigating to facebook
browserHistory.push("www.github.com"); // Current site

// Delete one entry -- Add it to forward stack to make it accessible
forward.push(browserHistory.pop()); // Returns www.github.com
// www.facebook.com is now our current site, we need to get back to github so ...
browserHistory.push(forward.pop());
// www.github.com is now our current site

// Clear forward stack when I navigate to a new site
while(forward.top() > -1){
	forward.pop();
}