Simple node js rest service that periodically reads battery and humidity

restiot.js

#!/usr/bin/env

var express = require('express');
const http = require('http');
var app = express();
var exec = require('exec');

const sensorMac = "<YOUR-DEVICE-MAC>";
const batteryChar = "00002a19-0000-1000-8000-00805f9b34fb";
const batteryHandler = "0x001b";
const humiditySensorHandler = "0x001f";
const humiditySensorChar = "00002a6f-0000-1000-8000-00805f9b34fb";

var sensorOutput = {
    battery: {},
    humidity: {}
};

app.get('/readmoisture', function (req, res) {
    res.json({
        humidity: humidityValue,
        lastRead: lastRead,
        battery: battery
    });
})

function readMoistureSensor() {
    readBleCharacteristic(humiditySensorChar, humiditySensorHandler, function (humidityVal) {
        if (humidityVal) {
            sensorOutput.humidity.lastRead = new Date();
            sensorOutput.humidity.value = Math.round(parseInt("0x" + humidityVal) * 100 / 256);
        }
    });
}

function readBattery() {
    readBleCharacteristic(batteryChar, batteryHandler, function (batteryVal) {
        if (batteryVal) {
            sensorOutput.battery.level = Math.round(parseInt("0x" + batteryVal));
            sensorOutput.battery.lastRead = new Date();
        }
    });
}

function readBleCharacteristic(characteristicUuid, handler, callback) {
    exec("gatttool -b " + sensorMac + " --char-read " + characteristicUuid + " -t random --handle=" + handler, function (err, out, code) {
        if (err instanceof Error)
            throw err;
        process.stderr.write(err);
        process.stdout.write(out);
        console.log(out);
        let output = out.replace('Characteristic value\/descriptor: ', '').trim();
        callback(output);
    });
}

setInterval(readMoistureSensor, 10000);
setInterval(readBattery, 5000);

var server = app.listen(80, function () {
    var host = server.address().address
    var port = server.address().port
    console.log("Simple rest service for iot listening at http://%s:%s", host, port)
})