Handle monitor(s) changes in Windows

gistFile.js

const { spawn } = require('child_process');

/**
 * Handle monitor(s) changes, ig, perform an action when a monitor is connected or disconnected.
 *
 * Notes:
 * - Windows implementation is based on Windows Management Interface (WMI) and WMI Query Language (WQL)
 *
 * Reference:
 * - https://stackoverflow.com/questions/5278860/using-wmi-to-identify-which-device-caused-a-win32-devicechangeevent
 * - https://msdn.microsoft.com/en-us/library/aa394651(v=vs.85).aspx
 * - http://wiki.splunk.com/Receive_events_whenever_someone_plugs/unplugs_a_USB_device
 * - https://msdn.microsoft.com/en-us/library/aa392902(v=vs.85).aspx
 *
 * @param handler {function} A function to handle monitor changes
 */
function onMonitorChanged(handler) {
    const MONITOR_CHANGED = 'monitor_changed';

    const wql = "SELECT * FROM __InstanceOperationEvent WITHIN 0.5 WHERE TargetInstance ISA 'Win32_PnPEntity' and TargetInstance.SERVICE = 'monitor'";
    const command = `Register-WMIEvent -Query "${wql}" -Action { Write-Host "${MONITOR_CHANGED}"} > $null`;
    const child = spawn('powershell.exe', [command]);
    child.stdout.on('data', (data) => {
        if (data.toString() === MONITOR_CHANGED) {
            handler();
        }
    });

    child.stderr.on('data', (data) => {
        logger.error(`Powershell Errors: ${data}`);
    });

    child.on('exit', () => {
        console.log('Powershell Script finished');
    });

    // child.stdin.end(); //end input
}

onMonitorChanged(() => console.log('monitor-changed'));