Example of syncing some redux state with a service worker

sw.js

const swSupported = !!('serviceWorker' in navigator)

const sendMessage = (messageData) => {
  if (!swSupported) {
    return
  }

  navigator.serviceWorker.controller.postMessage(messageData)
}

sendMessage({ sideway: window.sideway })

export const serviceWorkerMiddleware = (store) => (next) => (action) => {
  const result = next(action)
  if (action.type.indexOf('auth/') === 0) {
    sendMessage({ auth: store.getState().auth })
  }
  return result
}