const Config = {
  start: () => console.log('App has started'),
  update: () => console.log('App has updated'),
}

// We freeze the object to prevent new properties being added and existing properties being modified or removed
Object.freeze(Config)

Config.start() // "App has started"
Config.update() // "App has updated"

Config.name = "Robert" // We try to add a new key
console.log(Config)