function deviceNameSolution(devicenames) {

    let uniqueNames = new Set(devicenames);

    const nameOccurences = new Map(Array.from(uniqueNames).map(n => [n, 0]));

    let devices = [];
    for (let deviceName of devicenames) {
        let deviceOccurrenceCount = nameOccurences.get(deviceName);
        if (deviceOccurrenceCount === 0) {
            devices.push(deviceName);
        } else {
            devices.push(deviceName + deviceOccurrenceCount);
        }

        nameOccurences.set(deviceName, deviceOccurrenceCount + 1);
    }

    return devices;
}

deviceNameSolution(['switch', 'tv', 'switch', 'tv', 'tel', 'switch', 'tv']);