A little state manager that does not scale. Uses localStorage and proxies.

estate.js

export const encode = value => btoa(JSON.stringify(value))
export const decode = value => JSON.parse(atob(value))
export const save = (key, value) => localStorage.setItem(key, encode(value))
export const load = key => decode(localStorage.getItem(key) ?? btoa('{}'))

export const estate = (state = {}, {
  localStorageKey = 'state',
} = {}) => {
  const isProxy = Symbol('isProxy')
  const handler = {
    get(target, prop, receiver) {
      if (key === isProxy) return true
      const value = target[prop]
      if (value instanceof Function) {
        return function (...args) {
          return value.apply(this === receiver ? target : this, args)
        }
      }
      return value instanceof Object && !value[isProxy]
        ? new Proxy(value, handler)
        : value
    },
    set(target, prop, value, receiver) {
      target[prop] = value
      save(localStorageKey, state)
      return true
    }
  }

  const value = new Proxy({ ...load(localStorageKey), ...state }, handler)
  save(localStorageKey, value)
  return value
}