Deprecation Notice: Underlying providers are very unreliable currently. Specially the bitaps node is mostly on an older block number which causes production issues and seems that they've made breaking changes into their API. There is no meaning to use BlockCypher without purchasing their API keys due to their horrible rate limit criteria. I'll try to find and support more number of reliable BTC data providers and also incorporate a quorum logic to rule out out-of-sync/dishonest providers. Also, this library needs to be rewritten in TypeScript. I'm running very busy these days and cannot dedicate time to maintain this currently. So, I'm deprecating this package and do not advice it's use in production.

Bitcoin3js

Intends to be a complete Bitcoin Provider and Wallet Implementation. Currently, under development.

Installing

You can install Bitcoin3js in your project using npm.

npm install bitcoin3js

Quick Start with Provider

const bitcoin = require('bitcoin3js');
const provider = bitcoin.getDefaultProvider('test3');

// get latest block height
const blockNumber = await provider.getBlockHeight();

// get block by block height
const block = await provider.getBlock(1234);

// fetch balances in satoshis
const balance = await provider.getBalance('mwcxXm4jwz1K2hsrUJkbJ1YASC8Z4Vf4yB');

// get transactions of an address
const transactions = await provider.getTransactions('mwcxXm4jwz1K2hsrUJkbJ1YASC8Z4Vf4yB', {
  fromBlock: 1697117,
  toBlock: 1697117
});

// add an event
provider.on('block', blockNumber => {
  // do something
});

Providers

A provider instance is used to interact with the Bitcoin blockchain. Currently, there is integration of Blockcypher and Bitaps APIs.

Constructing a Provider Instance

const blockcypher = new bitcoin.providers.BlockcypherProvider('test3');
// or
const bitaps = new bitcoin.providers.BitapsProvider('test3');
// network: 'main' for bitcoin main network, 'test3' for bitcoin test network

Rate Limiters

Due to the presence of rate limits in the api providers, Bitcoin3js providers come with inbuilt rate limiters. You don't have to do anything. Though, you can customize the rate limiting variables.

const { BlockcypherProvider } = require('bitcoin3js/providers');

const blockcypher = new BlockcypherProvider({
  network: 'test3',
  apiKey: 'a3c1aad4c151458da9b1fdee2a7fbdf3',
  requestsLimit: 200,
  seconds: 60*60 // 1 hour
});

Fallback Providers

Fallback Provider aggregates multiple provider objects into one provider object and in event of the failure of one provider, it utilises other provider. It can also be used for load balancing between multiple providers.

const { FallbackProvider } = require('bitcoin3js/providers');

const provider = new FallbackProvider([ blockcypher, bitaps ], {
  loadBalancer: false // by default: true
});

The getDefaultProvider demonstrated in the beginning is a FallbackProvider with providers blockcypher and bitmaps.

MoveOn Mechanism

MoveOn mechanism comes inbuilt in a FallbackProvider. In some cases, an API call response is delayed, i.e. it doesn't resolve within a certain time, either due to server processing delay or delayed purposefully by the rate limiter (this happens a lot with BlockcypherProvider since it's got freedom for only 200 free calls in 1 hour, and if you are out of'em, it'd not resolve for a long time). So the MoveOn mechanism makes the Fallback provider move on to the next provider, if the call doesn't resolve within a specified moveOnDelay time.

The mechanism is active by default. Though it can be customized if needed.

const defaultProvider = bitcoin.getDefaultProvider({
  network: 'test3',
  moveOnDelay: 800 // by default: 1000
});
// or
const fallbackProvider = new FallbackProvider([ blockcypher, bitaps ], {
  moveOnDelay: 800
});

The end result is, a seamless bitcoin provider experience.

About

I've started this project mainly because couldn't find a reliable project related to bitcoin API providers. Definitely, there are plenty of online resources made available by providers like Blockcypher to work with Bitcoin APIs and most of the projects rely with a single API provider. If you're building a project which needs a reliable source of information, provider downtime is a factor to consider. Your project would have to rely that the provider will be online 100%, which of course might not be always possible. If you are ready to go few miles ahead, you need to do a complicated setup to rely on multiple API providers so that single point of failure won't be an issue. And from above you can see, the FallbackProvider is what that solves this problem.

Further Roadmap:

• More provider functionalities to be integrated
• A good documentation
• More provider apis to be integrated
• Essential helper methods to work in Bitcoin Ecosystem
• Wallet

Roadmap will be updated as development will follow. Any suggestions or contributions are welcome.