Simple hash router

hashrouter.js

/**
 * Simple router for switching between hash stings.
 * Suitable for MobX/Redux architecture and especially
 * handy for tabs, which is the reason why it exists.
 
  const state = { currentTab: 'lions' }  
 
  function activateTab(tabName) {
    // Dispatch state change
    state.currentTab = tabName
  }
  
  // Instantiate a router and set the index route
  // which is what get() will return when the hash is empty.
  const router = hashrouter('lions')
  router.listen(activateTab)
 
  <TabBar
    tabs={[
      { name: 'lions', label: 'Lions' },
      { name: 'tigers', label: 'Tigers' }
    ]}
    onSelect={ tab => router.go(tab.name) }
    selectedTab={ state.currentTab } />
 
 **/

const listeners = []

export default index => {

  function go(toRoute) {
    window.location.hash = toRoute
    notifyListeners()

    return get()
  }

  function get() {
    const current = window.location.hash.slice(1)
    return current.length > 0 ? current : index
  }

  function isActive(route) {
    return get() === route
  }

  function listen(listener) {
    listeners.push(listener)
  }

  function notifyListeners() {
    const cur = get()
    listeners.forEach(listener => listener(cur))
  }

  window.onhashchange = notifyListeners

  return {
    go,
    get,
    isActive,
    listen
  }
}