js获取当前网络状态（Wi-Fi 3G 4G）

getNetWorkType () {
      var ua = navigator.userAgent,
        networkStr = ua.match(/NetType\/\w+/) ? ua.match(/NetType\/\w+/)[0] : 'NetType/other'
      networkStr = networkStr.toLowerCase().replace('nettype/', '')
      var networkType
      switch (networkStr) {
        case 'wifi':
          networkType = 'wifi'
          break
        case '4g':
          networkType = '4g'
          break
        case '3g':
          networkType = '3g'
          break
        case '3gnet':
          networkType = '3g'
          break
        case '2g':
          networkType = '2g'
          break
        default:
          networkType = 'other'
      }
      return networkType
    }