Shared Tab Session

tabsession.js

'use strict'

const { each } = require('lodash')

incrementTabCount()
window.addEventListener('unload', decrementTabCount)

window.addEventListener('storage', (e) => {
  if (e.key === 'getSessionStorage') {
    // Some tab asked for the sessionStorage
    localStorage.setItem('sessionStorage', JSON.stringify(sessionStorage))
    localStorage.removeItem('sessionStorage')
  }
})

module.exports = {
  initSessionFromOpenTabs() {
    return new Promise((resolve) => {
      function handler(e) {
        if (e.key === 'sessionStorage') {
          each(JSON.parse(event.newValue), (v, k) => sessionStorage.setItem(k, v))
          window.removeEventListener('storage', handler)
          resolve()
        }
      }

      window.addEventListener('storage', handler)

      if (sessionStorage.length === 0 && getTabCount() > 1) {
        // Ask other tabs for session storage
        localStorage.setItem('getSessionStorage', Date.now())
      } else {
        resolve()
      }
    })
  }
}

function getTabCount() {
  return parseInt(localStorage.getItem('tabsOpen')) || 0
}

function setTabCount(n) {
  localStorage.setItem('tabsOpen', n)
}

function incrementTabCount() {
  setTabCount(getTabCount() + 1)
}

function decrementTabCount() {
  setTabCount(getTabCount() - 1)
}