text: var navigator = window && window.navigator
  var appVersion = (navigator && navigator.appVersion || '').toLowerCase()
  var userAgent = (navigator && navigator.userAgent || '').toLowerCase()
  var vendor = (navigator && navigator.vendor || '').toLowerCase()
  
  const comparator = {
    '<': (a, b) => { return a < b },
    '<=': (a, b) => { return a <= b },
    '>': (a, b) => { return a > b },
    '>=': (a, b) => { return a >= b }
  }
  
  module.exports = {
    toString: Object.prototype.toString,
    navigator,
    appVersion,
    userAgent,
    vendor,
    compareVersion (version, range) {
      var string = (range + '')
      var n = +(string.match(/\d+/) || NaN)
      var op = string.match(/^[<>]=?|/)[0]
      return comparator[op] ? comparator[op](version, n) : (version === n)
    }
  }
  