code: function parse() {
    var msie = /MSIE.(\d+)/i.exec(ua);
    var rv = /Trident.+rv:(\d+)/i.exec(ua);
    var version = msie || rv || undefined;
    return version ? +version[1] : version;
  }
docs: Get IE major version number
  
  @return {Number}
  @api private