Sum up the balances of a group of bitcoin addresses

btc-balance.js

const { Insight } = require('bitcore-explorers')
const promisify = require('tiny-promisify')

const addresses = [
  /* bitcoin addresses here! */
]

const insight = new Insight()
const getUnspentUtxosAsync = promisify(insight.getUnspentUtxos.bind(insight))

const BTC_SATOSHI = 100000000

function pick(array, prop) {
  return array.map(item => item[prop])
}

function sum(array, prop) {
  return pick(array, prop).reduce((acc, val) => acc + val, 0)
}

function getBalance(address) {
  return getUnspentUtxosAsync(address).then(utxos => ({
    address,
    satoshis: sum(utxos, 'satoshis')
  }))
}

Promise.all(addresses.map(getBalance)).then(function (balances) {
  balances.forEach(function ({ address, satoshis }) {
    console.log(`${address}: ${satoshis / BTC_SATOSHI}`)
  })
  const total = sum(balances, 'satoshis')
  console.log(`Total: ${total / BTC_SATOSHI}`)
})