utils/browser.js

/**
 * Detect browser running on private mode
 * @returns {Boolean}
 */
export function isPrivateMode() {
  return new Promise(function detect(resolve) {
    var yes = function () {
      resolve(true)
    } // is in private mode
    var not = function () {
      resolve(false)
    } // not in private mode

    function detectChromeOpera() {
      // https://developers.google.com/web/updates/2017/08/estimating-available-storage-space
      var isChromeOpera =
        /(?=.*(opera|chrome)).*/i.test(navigator.userAgent) &&
        navigator.storage &&
        navigator.storage.estimate
      if (isChromeOpera) {
        navigator.storage.estimate().then(function (data) {
          return data.quota < 120000000 ? yes() : not()
        })
      }
      return !!isChromeOpera
    }

    function detectFirefox() {
      var isMozillaFirefox = 'MozAppearance' in document.documentElement.style
      if (isMozillaFirefox) {
        if (indexedDB == null) yes()
        else {
          var db = indexedDB.open('inPrivate')
          db.onsuccess = not
          db.onerror = yes
        }
      }
      return isMozillaFirefox
    }

    function detectSafari() {
      var isSafari = navigator.userAgent.match(/Version\/([0-9\._]+).*Safari/)
      if (isSafari) {
        var testLocalStorage = function () {
          try {
            if (localStorage.length) not()
            else {
              localStorage.setItem('inPrivate', '0')
              localStorage.removeItem('inPrivate')
              not()
            }
          } catch (_) {
            // Safari only enables cookie in private mode
            // if cookie is disabled, then all client side storage is disabled
            // if all client side storage is disabled, then there is no point
            // in using private mode
            navigator.cookieEnabled ? yes() : not()
          }
          return true
        }

        var version = parseInt(isSafari[1], 10)
        if (version < 11) return testLocalStorage()
        try {
          window.openDatabase(null, null, null, null)
          not()
        } catch (_) {
          yes()
        }
      }
      return !!isSafari
    }

    function detectEdgeIE10() {
      var isEdgeIE10 =
        !window.indexedDB && (window.PointerEvent || window.MSPointerEvent)
      if (isEdgeIE10) yes()
      return !!isEdgeIE10
    }

    // when a browser is detected, it runs tests for that browser
    // and skips pointless testing for other browsers.
    if (detectChromeOpera()) return
    if (detectFirefox()) return
    if (detectSafari()) return
    if (detectEdgeIE10()) return

    // default navigation mode
    return not()
  })
}