GroganBurners / ferveo

(function () {

  'use strict';

  function emulatedIEMajorVersion() {

    var groups = /MSIE ([0-9.]+)/.exec(window.navigator.userAgent)

    if (groups === null) {

      return null

    }

    var ieVersionNum = parseInt(groups[1], 10)

    var ieMajorVersion = Math.floor(ieVersionNum)

    return ieMajorVersion

  }

  function actualNonEmulatedIEMajorVersion() {

    // Detects the actual version of IE in use, even if it's in an older-IE emulation mode.

    // IE JavaScript conditional compilation docs: http://msdn.microsoft.com/en-us/library/ie/121hztk3(v=vs.94).aspx

    // @cc_on docs: http://msdn.microsoft.com/en-us/library/ie/8ka90k2e(v=vs.94).aspx

    if (jscriptVersion === undefined) {

      return 11 // IE11+ not in emulation mode

    }

    if (jscriptVersion < 9) {

      return 8 // IE8 (or lower; haven't tested on IE<8)

    }

    return jscriptVersion // IE9 or IE10 in any mode, or IE11 in non-IE11 mode

  }

  var ua = window.navigator.userAgent

  if (ua.indexOf('Opera') > -1 || ua.indexOf('Presto') > -1) {

    return // Opera, which might pretend to be IE

  }

  var emulated = emulatedIEMajorVersion()

  if (emulated === null) {

    return // Not IE

  }

  var nonEmulated = actualNonEmulatedIEMajorVersion()

  if (emulated !== nonEmulated) {

    window.alert('WARNING: You appear to be using IE' + nonEmulated + ' in IE' + emulated + ' emulation mode.\nIE emulation modes can behave significantly differently from ACTUAL older versions of IE.\nPLEASE DON\'T FILE BOOTSTRAP BUGS based on testing in IE emulation modes!')

  }

})();