JSPM

import cookiesync from 'cookiesync'

/** Create an action that will trigger a sync to other tabs. */
const action = (userID, first, last) => ({ userID, first, last })

/** Create a handler that will run on all tabs that did not trigger the sync. */
const handler = (value, old, url) => {
  console.info(`Another tab at url ${url} switched user from "${old.first} ${old.last}" to "${value.first} ${value.last}".`)
  // do something with value.userID
}

/** Create a synchronizer. cookiesync supports N number of synchronizers for different things across your app. */
const usersync = cookiesync('user', action, handler)

/** Start synchronizing. */
usersync.start()

/** IE / Edge do not support local storage across multiple tabs. cookiesync will automatically fallback to a cookie polling mechanism here. You don't need to do anything else. */
if(usersync.isFallback)
  console.warn('browser doesnt support local storage synchronization, falling back to cookie synchronization.')

/** Trigger an action that will get handled on other tabs. */
usersync.trigger(1, 'jimmy', 'john')

setTimeout(() => {
  /** Trigger another action in 5 seconds. */
  usersync.trigger(2, 'jane', 'wonka')
}, 5000)

setTimeout(() => {
  /** If its still running, stop syncing in 10 seconds. */
  if(usersync.isRunning)
    usersync.stop()
}, 10000)

cookiesync(key: string, action: (...args) => payload, handler: payload => {}, [opts: Object]): { start, stop, trigger, isRunning, isFallback }