electrum-cash: working with balances

Introduction

Electrum-cash is a javascript/typescript library for communicating with electrum servers.

This example demonstrates how to get the balance of an address and how to get notified of changes to the balance of an address, using v1.4.3 of the electrum protocol.

To keep the example simple and clear, the code to set up and close a connection is omitted.

Fetch current balance

To get the current balance for an address, send a blockchain.address.get_balance request to the server with the address as the first parameter.

// The address we want to get balance for.
const address = 'qr4aadjrpu73d2wxwkxkcrt6gqxgu6a7usxfm96fst';

// Request the balance from the server.
const balance = await electrum.request('blockchain.address.get_balance', address);

// Print out the current balance, in satoshis.
console.log(`Balance for '${address}' is ${balance.confirmed} satoshis confirmed, and ${balance.unconfirmed} satoshis unconfirmed.`);

Example output for an existing wallet with a balance:

Balance for 'qr4aadjrpu73d2wxwkxkcrt6gqxgu6a7usxfm96fst' is 1165925 satoshis confirmed, and 0 satoshis unconfirmed.

Subscribe to balance changes

To subscribe to balance update notifications, send a blockchain.address.subscribe subscription to the server with the address as the first parameter, then request the updated balance any time the status of the address changes.

// The address we want to get balance updates for.
const address = 'qr4aadjrpu73d2wxwkxkcrt6gqxgu6a7usxfm96fst';

// Create a callback handler for balance updates.
const balanceUpdateHandler = async function(adress)
{
	// Request the balance from the server.
	const balance = await electrum.request('blockchain.address.get_balance', address);

	// Print out the updated balance, in satoshis.
	console.log(`Balance for '${address}' is ${balance.confirmed} satoshis confirmed, and ${balance.unconfirmed} satoshis unconfirmed.`);
}

// Subscribe to update notifications to the address status from the server.
const balance = await electrum.subscribe(balanceUpdateHandler.bind(this, address), 'blockchain.address.subscribe', address);

Example output when sending out all funds in the wallet:

Balance for 'qr4aadjrpu73d2wxwkxkcrt6gqxgu6a7usxfm96fst' is 1165925 satoshis confirmed, and 0 satoshis unconfirmed.

Balance for 'qr4aadjrpu73d2wxwkxkcrt6gqxgu6a7usxfm96fst' is 1165925 satoshis confirmed, and -1165925 satoshis unconfirmed.

Balance for 'qr4aadjrpu73d2wxwkxkcrt6gqxgu6a7usxfm96fst' is 0 satoshis confirmed, and 0 satoshis unconfirmed.