var TelegramBot = require('node-telegram-bot-api');
var exec = require('child_process').exec;
var BOT_TOKEN = 'token';
var bot = new TelegramBot(BOT_TOKEN, {polling: true});

var i = 1;
bot.onText(/\/photo/, function (msg) {
  console.log('photo');
  takePhoto(msg);
});

function takePhoto(msg) {         //  create a loop function
  setTimeout(function() {   //  call a 3s setTimeout when the loop is called
    console.log('taking photos');
    exec('raspistill -o /home/pi/pi-camera-bot/photos/$(date +%Y-%m-%d:%k:%M:%S).jpg');  //  your code here
    i++;                    //  increment the counter
    if (i < 4) {           //  if the counter < 10, call the loop function
      takePhoto(msg);//  ..  again which will trigger another
    }                       //  ..  setTimeout()
  }, 9000)
}