kasaControl.js

const { Client } = require('tplink-smarthome-api');
const _ = require('lodash');
const fs = require('fs');

const client = new Client();
const deviceInfoFilePath = '/tmp/devicelist.json';
var devicesInfo = {};

function writeStatusToFile(object) {
  // Write the status to file
  fs.writeFileSync(deviceInfoFilePath, JSON.stringify(object, null, 2));
};

function difference(object, base) {
  function changes(object, base) {
    return _.transform(object, function (result, value, key) {
      if (!_.isEqual(value, base[key])) {
        result[key] =
          _.isObject(value) && _.isObject(base[key])
            ? changes(value, base[key])
            : value;
      }
    });
  }
  return changes(base, object);
}

function isEmpty(obj) {
  for(var key in obj) {
      if(obj.hasOwnProperty(key))
          return false;
  }
  return true;
}

// Clean the device file at the first run.
fs.writeFileSync(deviceInfoFilePath, '');

// Search for all plugs and then write then to file
client.on('device-new', (device) => {
  device.startPolling(500);

  // Listen to the plug power event, update the cache file accordingly.
  device.on('power-update', (powerOn) => {
    const fileContents = fs.readFileSync(deviceInfoFilePath);
    if (fileContents == '') {
      writeStatusToFile(devicesInfo); 
    }
    // Update device info object
    if (!(device.host in devicesInfo)) {
      devicesInfo[device.host] = { name: device.alias, status: powerOn };
      writeStatusToFile(devicesInfo);
    }
    if (device.host in devicesInfo && powerOn != devicesInfo[device.host]['status']) {
      devicesInfo[device.host] = { name: device.alias, status: powerOn };
      writeStatusToFile(devicesInfo);
    }
  });
});

console.log('Start discovering devices');
client.startDiscovery({ discoveryTimeout: 0 });
console.log('Finished discovering devices');

fs.watchFile(deviceInfoFilePath, () => {
  const fileContents = fs.readFileSync(deviceInfoFilePath);
  const newDevicesInfo = JSON.parse(fileContents);
  const diff = difference(devicesInfo, newDevicesInfo);
  devicesInfo = newDevicesInfo;
  if (!isEmpty(diff)) {
    // Send the new status to the device
    for (const key in diff) {
      const plug = client.getPlug({ host: key });
      console.log(`Devices status have been updated`);
      plug.setPowerState(diff[key]['status']);
    }
  }
});

package.json

{
  "name": "kasacontrol",
  "version": "1.0.0",
  "description": "",
  "main": "kasaControl.js",
  "scripts": {
    "start": "node kasaControl.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "dongfeng gu",
  "license": "ISC",
  "dependencies": {
    "lodash": "^4.17.15",
    "tplink-smarthome-api": "^2.0.0"
  }
}