Skip to main content

Geth JavaScript Console Guide

Use this guide to learn how to set up and use the Geth JS console with an Evmos node.

Go-ethereum responds to instructions encoded as JSON objects as defined in the JSON-RPC-API. To perform and test these instructions, developers can use tools like curl. However, this is a low level and rather error-prone way to interact with the node. Most developers prefer to use convenient libraries that abstract away some of the more tedious and awkward tasks such as converting values from hexadecimal strings into numbers, or converting between denominations of ether (Wei, Gwei, etc). One such library is Web3.js. The purpose of Geth’s Javascript console is to provide a built-in environment to use a subset of the Web3.js libraries to interact with a Geth node. You can use this powerful tool to interact with an Evmos node too!

Prerequisite readings

Installing Go-Ethereum

Install the Go-ethereum CLI (geth) following the procedure corresponding to your OS in the geth docs. This will include the Javascript console.

Check that the installation was successful by running the following command:

geth version

If everything went as expected, you should have an output similar to this:

Version: 1.10.26-stable
Git Commit: e5eb32acee19cc9fca6a03b10283b7484246b15a
Architecture: amd64
Go Version: go1.18.5
Operating System: linux

Install dependencies

Make sure you have installed all the dependencies mentioned in the Prerequisite Readings section.

Run Evmos local node

  • Clone the evmos repository (if you haven’t already)
  • Run the script to start a local node
git clone
cd evmos

Attach geth JS console

Wait a few seconds for the node to start up the JSON-RPC server. The local node has the HTTP-RPC server enabled and is listening at port 8545 by default. Attach a geth console to your node with the following command:

 $ geth attach
Welcome to the Geth JavaScript console!

instance: Version dev ()
Compiled at using Go go1.19.2 (amd64)
coinbase: 0x7771fD5e52cf6A81B49d7EF40Bfc2bd0eA8A92E6
at block: 975 (Fri Nov 25 2022 01:21:52 GMT-0300 (-03))
modules: debug:1.0 eth:1.0 net:1.0 personal:1.0 rpc:1.0 txpool:1.0 web3:1.0

To exit, press ctrl-d or type exit

Use JSON-RPC methods

Now we can use all implemented JSON-RPC methods. Find an exhaustive list of the supported JSON-RPC methods on Evmos docs.

Below are some examples of how to use the console.

Check current block height

We can check the current block height of the chain:

> eth.blockNumber
> eth.blockNumber

Get accounts

Get an array of the existing accounts in the keyring. To do so, use the following method:

> eth.accounts
["0xf0c3878dd8de6edc0702c06c2bb9a8e380397173", "0xfdd268dfeca95cff23ba385dec161defea031682", "0x35ab07f08f9af9166e9225b3407ad5e63756a084", "0x6a36c1efef7dd58981b3999217cdb3ae720cf330"]

Get chain id

We can get the chain id using:

> net.version

Check balances

Check any account balance using the eth.getBalance method:

> eth.getBalance(eth.accounts[0])

We get a big number because the result is denominated in aevmos. We can convert to Evmos (10 ^18 aevmos) using the web3.fromWei method:

> web3.fromWei(eth.getBalance(eth.accounts[0]),"ether")

Send transactions

We can perform token transfers using the corresponding method. For example, let's transfer 1 Evmos token from our account to another account:

> eth.sendTransaction({from:eth.accounts[0], to: eth.accounts[1], value: web3.toWei(1, "ether")})

As a response, we get back the transaction hash.

Now we can check the balance of the sender and receiver accounts.

The sender balance is reduced by 1 Evmos token and the fees paid for the transaction:

> web3.fromWei(eth.getBalance(eth.accounts[0]),"ether")

The receiver account balance initially was 100000000 Evmos tokens. After the transaction, the account balance has increased by 1 Evmos token.

> web3.fromWei(eth.getBalance(eth.accounts[1]),"ether")

🚪 Exit geth console

To exit the geth console use:

 > exit

or type Ctrl + D.

🪄 Tips & tricks

List commands

A small trick to see the list of initial commands. Type 2 spaces then hit TAB twice. You will get:

AggregateError Function Object TypeError _consoleWeb3Transport encodeURIComponent loadScript toLocaleString
Array GoError Promise URIError _setInterval escape message toString
ArrayBuffer Infinity Proxy Uint16Array _setTimeout eth net txpool
BigNumber Int16Array RangeError Uint32Array clearInterval eval parseFloat undefined
Boolean Int32Array ReferenceError Uint8Array clearTimeout globalThis parseInt unescape
DataView Int8Array Reflect Uint8ClampedArray console hasOwnProperty personal valueOf
Date JSON RegExp WeakMap constructor inspect propertyIsEnumerable web3
Error Map Set WeakSet debug isFinite require
EvalError Math String Web3 decodeURI isNaN rpc
Float32Array NaN Symbol XMLHttpRequest decodeURIComponent isPrototypeOf setInterval
Float64Array Number SyntaxError __proto__ encodeURI jeth setTimeout

The same applies to the different namespaces. For example, you can type eth. and hit TAB twice. You will get:

> eth.
eth._requestManager eth.fillTransaction eth.getGasPrice eth.getTransaction eth.protocolVersion
eth.accounts eth.filter eth.getHashrate eth.getTransactionCount eth.resend
eth.blockNumber eth.gasPrice eth.getHeaderByHash eth.getTransactionFromBlock eth.sendIBANTransaction eth.getAccounts eth.getHeaderByNumber eth.getTransactionReceipt eth.sendRawTransaction
eth.chainId eth.getBalance eth.getLogs eth.getUncle eth.sendTransaction
eth.coinbase eth.getBlock eth.getMaxPriorityFeePerGas eth.getWork eth.sign
eth.compile eth.getBlockByHash eth.getMining eth.hashrate eth.signTransaction
eth.constructor eth.getBlockByNumber eth.getPendingTransactions eth.iban eth.submitTransaction
eth.contract eth.getBlockNumber eth.getProof eth.icapNamereg eth.submitWork
eth.createAccessList eth.getBlockTransactionCount eth.getProtocolVersion eth.isSyncing eth.syncing
eth.defaultAccount eth.getBlockUncleCount eth.getRawTransaction eth.maxPriorityFeePerGas
eth.defaultBlock eth.getCode eth.getRawTransactionFromBlock eth.mining
eth.estimateGas eth.getCoinbase eth.getStorageAt eth.namereg
eth.feeHistory eth.getCompilers eth.getSyncing eth.pendingTransactions