Listen to balance changes

This example shows how to instantiate a Polkadot API object and use it to connect to a node.

const Api = require('@polkadot/api').default
const WsProvider = require('@polkadot/api-provider/ws').default
const storage = require('@polkadot/storage').default
const BN = require('bn.js')
const provider = new WsProvider('ws://127.0.0.1:9944')
const api = new Api(provider)
const Alice = '5GoKvZWG5ZPYL1WUovuHW3zJBWBP5eT8CbqjdRY4Q6iMaDtZ'

console.log('You may let this example running and start the example 06 or send DOTs to ' + Alice)

api.state
  .storage([[storage.staking.public.freeBalanceOf, Alice]], (_, values) => {
    console.log(`Balance of ${Alice}: ${new BN(values[0]).toString(10)} DOTs`)
  })
  .then((subscriptionId) => {
    console.log('Balance changes subscription id:', subscriptionId)
  })