simple btc address monitor

btcmonitor.js

var address = process.env.BTC_ADDR;
if(!address) {
  throw err('Provide btc address');
}
var request = require('request');
var f; // set interval ref;
var BTC_URL = 'https://blockchain.info/address/' + address + '?format=json';

var balance;

function checkBalance(){
  request(BTC_URL, function(err, res, body){
    if(err){
      throw err;
    }
    if(body && body.final_balance && balance) { // if successful and balance already set
      var diff = Math.abs(balance - body.final_balance);
      if(diff > 0) {
        console.log('balance changed');
        f = null;
        doSomethingElse(); // trigger something else.
      }
    } else { // else set initial balance
      balance = body.final_balance;
      console.log('Setting initial balance');
    }
  });
}

f = setInterval(checkBalance, 5000); // run every 5 seconds.

//usage: BTC_ADDR=<btcaddr> node btcmonitor.js