js随机生成36位字符

uuid () {
  var s = []
  var hexDigits = '0123456789abcdef'
  for (var i = 0; i < 36; i++) {
    s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1)
  }
  s[14] = '4'
  s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1)
  s[8] = s[13] = s[18] = s[23]
  var uuidA = s.join('')
  return uuidA
}