eth-block-tracker

This module walks the Ethereum blockchain, keeping track of the latest block. It uses a web3 provider as a data source and will continuously poll for the next block.

const HttpProvider = require('ethjs-provider-http')
const BlockTracker = require('eth-block-tracker')

const provider = new HttpProvider('https://mainnet.infura.io')
const blockTracker = new BlockTracker({ provider })
blockTracker.on('block', console.log)
blockTracker.start()

methods

new BlockTracker({ provider, pollingInterval })

creates a new block tracker with provider as a data source and pollingInterval (ms) timeout between polling for the latest block.

getCurrentBlock()

synchronous returns the current block. may be null.

console.log(blockTracker.getCurrentBlock())

awaitCurrentBlock()

Returns a promise. asynchronously returns the current block. if not yet available, it will wait until it has the latest block.

start({ fromBlock })

Start walking from the fromBlock (default: 'latest') forward. fromBlock should be a number as a hex encoded string. Returns a promise which is rejected if an error in encountered.

blockTracker.start()

blockTracker.start({ fromBlock: '0x00' })

stop()

Stop walking the blockchain.

blockTracker.stop()

EVENTS

block

The block event is emitted for every block in order. Use this event if you want to operate on every block without missing any.

blockTracker.on('block', (newBlock) => console.log(newBlock))

latest

The latest event is emitted for every that is detected to be the latest block. This means skipping a block if there were two created since the last polling period. Use this event if you don't care about stale blocks.

blockTracker.on('latest', (newBlock) => console.log(newBlock))

sync

The sync event is emitted the same as "latest" but includes the previous block.

blockTracker.on('sync', ({ newBlock, oldBlock }) => console.log(newBlock, oldBlock))

NOTES

Does not currently handle block reorgs.