NetInfo

enum DeviceNetworkType {
    Unknown,
    None,
    Wifi,
    Mobile2G,
    Mobile3G,
    Mobile4G
}

// Returns a promise that specifies whether the device currently
// has network connectivity
isConnected(): SyncTasks.Promise<boolean>;

// Returns the type of network
getType(): SyncTasks.Promise<DeviceNetworkType>;

// Triggered when the connectivity changes
connectivityChangedEvent: SubscribableEvent<(isConnected: boolean) => void>;

private isConnected: boolean;

constructor() {
    // Query the initial connectivity state.
    this.isConnected = false;
    RXNetInfo.isConnected().then(isConnected => {
        this.isConnected = isConnected;
    });

    RXNetInfo.connectivityChangedEvent.subscribe(isConnected => {
        // Update the connectivity state.
        this.isConnected = isConnected;
    });
}