# The Problem
I accidently encountered a problem during the development of the 2.0 version of [simstate](/articles/simstate-and-why): During an iteration of a set of `observers` stored in a ES6 Map,
# What is it?
[![npm](https://img.shields.io/npm/v/simstate.svg?style=flat-square)](https://www.npmjs.com/package/simstate)
[![types](https://img.shields.io/npm/types/simstate.svg?style=flat-square)
# Introduction
Security/safety and extensibility/scalability are two pairs of quality attributes that is of great importance in software architecture. This articles discusses about their definitions