@ethereumjs/blockchain v10

Stores a sequential chain of @ethereumjs/block blocks, tracks the canonical head, and supports reorgs via putBlock(). Used by @ethereumjs/client and @ethereumjs/vm.

Runnable examples live in examples/.

Table of Contents

• Installation
• Getting Started
• Block Lookup
• Chain Iteration
• Hardfork by Head
• Custom Genesis
• Consensus Types
• Supported Block Features
• Events and Debugging
• Browser
• API
• EthereumJS
• License

Installation

npm install @ethereumjs/blockchain

Getting Started

Use createBlockchain() — it awaits async initialization (genesis setup, consensus wiring):

import { createBlockchain } from '@ethereumjs/blockchain'
import { Common, Mainnet } from '@ethereumjs/common'

const common = new Common({ chain: Mainnet })
const blockchain = await createBlockchain({ common })
console.log(`Genesis hash: ${blockchain.genesisBlock.hash()}`)

Main constructors: createBlockchain(), createBlockchainFromBlocksData().

Pass validateBlocks: false / validateConsensus: false in examples and tests when blocks are intentionally incomplete.

Block Lookup

Retrieve blocks by number or hash after adding them with putBlock():

// ./examples/getBlock.ts

import { createBlock } from '@ethereumjs/block'
import { createBlockchain } from '@ethereumjs/blockchain'
import { Common, Hardfork, Mainnet } from '@ethereumjs/common'
import { bytesToHex } from '@ethereumjs/util'

const main = async () => {
  const common = new Common({ chain: Mainnet, hardfork: Hardfork.Prague })
  const blockchain = await createBlockchain({
    validateBlocks: false,
    validateConsensus: false,
    common,
  })

  const block1 = createBlock(
    {
      header: {
        number: 1n,
        parentHash: blockchain.genesisBlock.hash(),
        difficulty: blockchain.genesisBlock.header.difficulty + 1n,
      },
    },
    { common, setHardfork: true },
  )
  const block2 = createBlock(
    {
      header: {
        number: 2n,
        parentHash: block1.header.hash(),
        difficulty: block1.header.difficulty + 1n,
      },
    },
    { common, setHardfork: true },
  )
  await blockchain.putBlock(block1)
  await blockchain.putBlock(block2)

  const byNumber = await blockchain.getBlock(2n)
  const byHash = await blockchain.getBlock(block2.hash())

  console.log(`Block ${byNumber.header.number} hash: ${bytesToHex(byNumber.hash())}`)
  console.log(`Lookup by hash matches: ${bytesToHex(byHash.hash()) === bytesToHex(block2.hash())}`)
}

void main()

Also: getBlocks(), getIteratorHead(), getLatestHeader().

Chain Iteration

Walk the canonical chain with iterator():

// ./examples/iterateChain.ts

import { createBlock } from '@ethereumjs/block'
import { createBlockchain } from '@ethereumjs/blockchain'
import { Common, Hardfork, Mainnet } from '@ethereumjs/common'
import { bytesToHex } from '@ethereumjs/util'

const main = async () => {
  const common = new Common({ chain: Mainnet, hardfork: Hardfork.Prague })
  const blockchain = await createBlockchain({
    validateBlocks: false,
    validateConsensus: false,
    common,
  })

  const block = createBlock(
    {
      header: {
        number: 1n,
        parentHash: blockchain.genesisBlock.hash(),
        difficulty: blockchain.genesisBlock.header.difficulty + 1n,
      },
    },
    { common, setHardfork: true },
  )
  const block2 = createBlock(
    {
      header: {
        number: 2n,
        parentHash: block.header.hash(),
        difficulty: block.header.difficulty + 1n,
      },
    },
    { common, setHardfork: true },
  )
  await blockchain.putBlock(block)
  await blockchain.putBlock(block2)

  await blockchain.iterator('i', (block) => {
    const blockNumber = block.header.number.toString()
    const blockHash = bytesToHex(block.hash())
    console.log(`Block ${blockNumber}: ${blockHash}`)
  })
}
void main()

Hardfork by Head

Pin Common hardfork to the current head block number on init:

// ./examples/hardforkByHead.ts

import { createBlockchain } from '@ethereumjs/blockchain'
import { Common, Mainnet } from '@ethereumjs/common'

const main = async () => {
  const common = new Common({ chain: Mainnet })
  await createBlockchain({ common, hardforkByHeadBlockNumber: true })
  console.log(`Hardfork at genesis head: ${common.hardfork()}`)
}

void main()

Custom Genesis

Build a chain from a Geth genesis JSON file:

// ./examples/gethGenesis.ts

import { createBlockchain } from '@ethereumjs/blockchain'
import { createCommonFromGethGenesis, parseGethGenesisState } from '@ethereumjs/common'
import { postMergeGethGenesis } from '@ethereumjs/testdata'
import { bytesToHex } from '@ethereumjs/util'

const main = async () => {
  const common = createCommonFromGethGenesis(postMergeGethGenesis, { chain: 'customChain' })
  const genesisState = parseGethGenesisState(postMergeGethGenesis)
  const blockchain = await createBlockchain({
    genesisState,
    common,
  })
  const genesisBlockHash = blockchain.genesisBlock.hash()
  common.setForkHashes(genesisBlockHash)
  console.log(
    `Genesis hash from geth genesis parameters - ${bytesToHex(blockchain.genesisBlock.hash())}`,
  )
}

void main()

Built-in network genesis state lives in @ethereumjs/genesis. Access the genesis block via blockchain.genesisBlock.

Consensus Types

Clique example:

// ./examples/clique.ts

import { CliqueConsensus, createBlockchain } from '@ethereumjs/blockchain'
import { Common, ConsensusAlgorithm, Hardfork } from '@ethereumjs/common'
import { goerliChainConfig } from '@ethereumjs/testdata'

import type { ConsensusDict } from '@ethereumjs/blockchain'

const main = async () => {
  const common = new Common({ chain: goerliChainConfig, hardfork: Hardfork.London })

  const consensusDict: ConsensusDict = {}
  consensusDict[ConsensusAlgorithm.Clique] = new CliqueConsensus()
  const blockchain = await createBlockchain({
    consensusDict,
    common,
  })
  console.log(`Created blockchain with ${blockchain.consensus!.algorithm} consensus algorithm`)
}

void main()

Custom consensus: implement the Consensus interface and pass via consensusDict or consensus option. See customConsensus.spec.ts.

Storage

Default DB is in-memory MapDB. For persistence, pass a DB-conforming backend (see @ethereumjs/client level wrapper).

Supported Block Features

• EIP-1559 — base fee blocks (default post-London)
• EIP-4844 — blob txs (requires KZG on Common, see @ethereumjs/tx)
• EIP-7685 — CL requests in block headers
• EIP-4895 — withdrawals

Events and Debugging

blockchain.events emits deletedCanonicalBlocks on reorgs.

Debug loggers: blockchain:#, blockchain:clique, blockchain:ethash. Enable with DEBUG=ethjs,blockchain:clique.

Browser

Hybrid ESM/CJS builds are provided. See ./examples/browser.html.

API

Generated TypeDoc documentation.

EthereumJS

The EthereumJS GitHub organization and its repositories are managed by members of the former Ethereum Foundation JavaScript team and the broader Ethereum community. If you want to join for work or carry out improvements on the libraries see the developer docs for an overview of current standards and tools and review our code of conduct.

License

MPL-2.0