@ethereumjs/common

What is @ethereumjs/common?

@ethereumjs/common is a JavaScript library that provides common Ethereum constants, parameters, and functions. It is used to define and manage chain and hardfork parameters, making it easier to work with different Ethereum networks and their respective upgrades.

What are @ethereumjs/common's main functionalities?

Chain and Hardfork Parameters

This feature allows you to define and manage chain and hardfork parameters. The code sample demonstrates how to create a Common instance for the Ethereum mainnet with the 'istanbul' hardfork.

const Common = require('@ethereumjs/common').default;
const mainnetCommon = new Common({ chain: 'mainnet', hardfork: 'istanbul' });
console.log(mainnetCommon.chainName()); // 'mainnet'
console.log(mainnetCommon.hardfork()); // 'istanbul'

Custom Chains

This feature allows you to define custom chain parameters. The code sample demonstrates how to create a Common instance for a custom chain with specific chain and network IDs.

const Common = require('@ethereumjs/common').default;
const customChainParams = { name: 'custom', chainId: 1234, networkId: 1234 };
const customCommon = Common.forCustomChain('mainnet', customChainParams, 'istanbul');
console.log(customCommon.chainId()); // 1234

EIP Activation

This feature allows you to check if a specific Ethereum Improvement Proposal (EIP) is activated for a given hardfork. The code sample demonstrates how to check if EIP-1559 is activated for the 'berlin' hardfork.

const Common = require('@ethereumjs/common').default;
const common = new Common({ chain: 'mainnet', hardfork: 'berlin' });
console.log(common.isActivatedEIP(1559)); // true or false depending on the EIP and hardfork

Other packages similar to @ethereumjs/common

web3

web3.js is a collection of libraries that allow you to interact with a local or remote Ethereum node using HTTP, IPC, or WebSocket. While it provides broader functionality for interacting with the Ethereum blockchain, it does not focus specifically on chain and hardfork parameters like @ethereumjs/common.

ethers

ethers.js is a library for interacting with the Ethereum blockchain and its ecosystem. It provides utilities for signing transactions, interacting with smart contracts, and more. Similar to web3.js, it offers a broader range of functionalities but does not specialize in chain and hardfork parameters.

ethjs

ethjs is a highly modular, lightweight library for interacting with the Ethereum blockchain. It provides basic functionalities for sending transactions, interacting with contracts, and more. However, it does not offer the same level of detail for chain and hardfork parameters as @ethereumjs/common.

README

@ethereumjs/common

Resources common to all EthereumJS implementations.

Note: this README reflects the state of the library from v2.0.0 onwards. See README from the standalone repository for an introduction on the last preceding release.

INSTALL

npm install @ethereumjs/common

USAGE

All parameters can be accessed through the Common class which can be required through the main package and instantiated either with just the chain (e.g. 'mainnet') or the chain together with a specific hardfork provided.

If no hardfork is provided, the common is initialized with the default hardfork.

Current DEFAULT_HARDFORK: istanbul

Here are some simple usage examples:

import Common from '@ethereumjs/common'

// Instantiate with the chain (and the default hardfork)
const c = new Common({ chain: 'ropsten' })
c.param('gasPrices', 'ecAddGas') // 500

// Chain and hardfork provided
c = new Common({ chain: 'ropsten', hardfork: 'byzantium' })
c.param('pow', 'minerReward') // 3000000000000000000

// Instantiate with an EIP activated
const c = new Common({ chain: 'mainnet', eips: [2537] })

// Access genesis data for Ropsten network
c.genesis().hash // 0x41941023680923e0fe4d74a34bdac8141f2540e3ae90623718e47d66d1ca4a2d

// Get bootstrap nodes for chain/network
c.bootstrapNodes() // Array with current nodes

If the initializing library only supports a certain range of hardforks you can use the supportedHardforks option to restrict hardfork access on the Common instance:

const c = new Common({
  chain: 'ropsten',
  supportedHardforks: ['byzantium', 'constantinople', 'petersburg'],
})

This will e.g. throw an error when a param is requested for an unsupported hardfork and like this prevents unpredicted behaviour.

For an improved developer experience, there are Chain and Hardfork enums available:

import Common, { Chain, Hardfork } from '@ethereumjs/common'

// Chain provided by Chain enum
const c = new Common({ chain: Chain.Mainnet })

// Chain provided by Chain enum, hardfork provided by Hardfork enum
const c = new Common({ chain: Chain.Ropsten, hardfork: Hardfork.Byzantium })

API

See the API documentation for a full list of functions for accessing specific chain and depending hardfork parameters. There are also additional helper functions like paramByBlock (topic, name, blockNumber) or hardforkIsActiveOnBlock (hardfork, blockNumber) to ease blockNumber based access to parameters.

• API Docs

EVENTS

The Common class is implemented as an EventEmitter and is emitting the following events on which you can react within your code:

Event	Description
hardforkChanged	Emitted when a hardfork change occurs in the Common object

SETUP

Chains

The chain can be set in the constructor like this:

const c = new Common({ chain: 'ropsten' })

Or optionally with the Chain enum:

import Common, { Chain } from '@ethereumjs/common'

const c = new Common({ chain: Chain.Ropsten })

Supported chains:

• mainnet (Chain.Mainnet)
• ropsten (Chain.Ropsten)
• rinkeby (Chain.Rinkeby)
• kovan (Chain.Kovan)
• goerli (Chain.Goerli)
• sepolia (Chain.Sepolia) (v2.6.1+)
• Private/custom chain parameters

The following chain-specific parameters are provided:

• name
• chainId
• networkId
• consensusType (e.g. pow or poa)
• consensusAlgorithm (e.g. ethash or clique)
• consensusConfig (depends on consensusAlgorithm, e.g. period and epoch for clique)
• genesis block header values
• hardforks block numbers
• bootstrapNodes list
• dnsNetworks list (EIP-1459-compliant list of DNS networks for peer discovery)

To get an overview of the different parameters have a look at one of the chain-specifc files like mainnet.json in the chains directory, or to the Chain type in ./src/types.ts.

Working with private/custom chains

There are two distinct APIs available for setting up custom(ized) chains.

Basic Chain Customization / Predefined Custom Chains

There is a dedicated Common.custom() static constructor which allows for an easy instantiation of a Common instance with somewhat adopted chain parameters, with the main use case to adopt on instantiating with a deviating chain ID (you can use this to adopt other chain parameters as well though). Instantiating a custom common instance with its own chain ID and inheriting all other parameters from mainnet can now be as easily done as:

const common = Common.custom({ chainId: 1234 })

The custom() method also takes a string as a first input (instead of a dictionary). This can be used in combination with the CustomChain enum dict which allows for the selection of predefined supported custom chains for an easier Common setup of these supported chains:

const common = Common.custom(CustomChain.ArbitrumRinkebyTestnet)

The following custom chains are currently supported:

• PolygonMainnet
• PolygonMumbai
• ArbitrumRinkebyTestnet
• xDaiChain
• OptimisticKovan
• OptimisticEthereum

Common instances created with this simplified custom() constructor can't be used in all usage contexts (the HF configuration is very likely not matching the actual chain) but can be useful for specific use cases, e.g. for sending a tx with @ethereumjs/tx to an L2 network (see the Tx library README for a complete usage example).

Activate with a single custom Chain setup

If you want to initialize a Common instance with a single custom chain which is then directly activated you can pass a dictionary - conforming to the parameter format described above - with your custom chain values to the constructor using the chain parameter or the setChain() method, here is some example:

import myCustomChain from './[PATH]/myCustomChain.json'
const common = new Common({ chain: myCustomChain })

Initialize using customChains Array

A second way for custom chain initialization is to use the customChains constructor option. This option comes with more flexibility and allows for an arbitrary number of custom chains to be initialized on a common instance in addition to the already supported ones. It also allows for an activation-independent initialization, so you can add your chains by adding to the customChains array and either directly use the chain option to activate one of the custom chains passed or activate a build in chain (e.g. mainnet) and switch to other chains - including the custom ones - by using Common.setChain().

import myCustomChain1 from './[PATH]/myCustomChain1.json'
import myCustomChain2 from './[PATH]/myCustomChain2.json'
// Add two custom chains, initial mainnet activation
const common1 = new Common({ chain: 'mainnet', customChains: [ myCustomChain1, myCustomChain2 ] })
// Somewhat later down the road...
common1.setChain('customChain1')
// Add two custom chains, activate customChain1
const common1 = new Common({ chain: 'customChain1', customChains: [ myCustomChain1, myCustomChain2 ] })

It is also possible (v2.5.0+) to pass in a custom genesis state file (see e.g. src/genesisStates/goerli.json for an example on the format needed) along with the custom chain configuration:

import myCustomChain1 from '[PATH_TO_MY_CHAINS]/myCustomChain1.json'
import chain1GenesisState from '[PATH_TO_GENESIS_STATES]/chain1GenesisState.json'
const common = new Common({ chain: 'myCustomChain1', customChains: [ [ myCustomChain1, chain1GenesisState ] ]})

Accessing the genesis state can be done as follows:

const genesisState = common.genesisState()

This now also provides direct access to custom genesis states passed into Common as described above. The old Common-separate genesisStateByName() and genesisStateById() functions are now deprecated and usage should be avoided.

Hardforks

The hardfork can be set in constructor like this:

const c = new Common({ chain: 'ropsten', hardfork: 'byzantium' })

Or optionally with the Hardfork enum:

import Common, { Chain, Hardfork } from '@ethereumjs/common'

const c = new Common({
  chain: Chain.Ropsten,
  hardfork: Hardfork.Byzantium,
})

Active Hardforks

There are currently parameter changes by the following past and future hardfork by the library supported:

• chainstart (Hardfork.Chainstart)
• homestead (Hardfork.Homestead)
• dao (Hardfork.Dao)
• tangerineWhistle (Hardfork.TangerineWhistle)
• spuriousDragon (Hardfork.SpuriousDragon)
• byzantium (Hardfork.Byzantium)
• constantinople (Hardfork.Constantinople)
• petersburg (Hardfork.Petersburg) (aka constantinopleFix, apply together with constantinople)
• istanbul (Hardfork.Instanbul) (DEFAULT_HARDFORK (v2.0.0 release series))
• muirGlacier (Hardfork.MuirGlacier)
• berlin (Hardfork.Berlin) (since v2.2.0)
• london (Hardfork.London) (since v2.4.0)
• merge (Hardfork.Merge) (since v2.5.0, experimental)

Future Hardforks

The next upcoming HF shanghai is currently not yet supported by this library.

Parameter Access

For hardfork-specific parameter access with the param() and paramByBlock() functions you can use the following topics:

• gasConfig
• gasPrices
• vm
• pow

See one of the hardfork files like byzantium.json in the hardforks directory for an overview. For consistency, the chain start (chainstart) is considered an own hardfork.

The hardfork-specific json files only contain the deltas from chainstart and shouldn't be accessed directly until you have a specific reason for it.

EIPs

Starting with the v2.0.0 release of the library, EIPs are now native citizens within the library and can be activated like this:

const c = new Common({ chain: Chain.Mainnet, eips: [2537] })

The following EIPs are currently supported:

• EIP-1559: Fee market change for ETH 1.0 chain
• EIP-2315: Simple subroutines for the EVM
• EIP-2537: BLS precompiles
• EIP-2565: ModExp gas cost
• EIP-2718: Transaction Types
• EIP-2929: gas cost increases for state access opcodes
• EIP-2930: Optional accesss list tx type
• EIP-3198: Base fee Opcode
• EIP-3529: Reduction in refunds
• EIP-3541: Reject new contracts starting with the 0xEF byte
• EIP-3554: Difficulty Bomb Delay to December 2021 (only PoW networks)
• EIP-3675: Upgrade consensus to Proof-of-Stake (experimental)
• EIP-3855: Push0 opcode (v2.6.1+)

Bootstrap Nodes

You can use common.bootstrapNodes() function to get nodes for a specific chain/network.

EthereumJS

See our organizational documentation for an introduction to EthereumJS as well as information on current standards and best practices.

If you want to join for work or do improvements on the libraries have a look at our contribution guidelines.

LICENSE

MIT