Klaytn Docs Archive
Getting StartedBuild a dAppNode OperationDeveloper Hub
  • Klaytn Docs
  • -
    • Klaytn Overview
      • Why Klaytn
      • Klaytn Design
        • Consensus Mechanism
        • Accounts
        • Transactions
          • Basic
          • Fee Delegation
          • Partial Fee Delegation
          • Ethereum
        • Computation
          • Klaytn Smart Contract
          • Execution Model
          • Computation Cost
            • Computation Cost (Previous docs)
          • Klaytn Virtual Machine
            • Klaytn Virtual Machine (Previous docs)
        • Storage
          • State Migration
          • StateDB Live Pruning
        • Transaction Fees
          • Transaction Fees (Previous docs)
        • Klaytn native coin - KLAY
        • Token Economy
        • Governance
        • Multi-Channel
        • KNI
      • Scaling Solutions
    • Getting Started
      • Deploying Smart Contract Using Foundry
      • Deploying Smart Contract Using Hardhat
      • Deploying Smart Contract Using Thirdweb
      • Deploying Smart Contract Using KEN
        • Launch an Endpoint Node
        • Top up your Account
        • Install Development Tools
        • Deploy a Smart Contract
        • Check the Deployment
        • Account Management
          • Creating Accounts
          • Managing Accounts
      • Development Environment
      • Getting KLAY
    • Smart Contract
      • Solidity - Smart Contract Language
      • Precompiled Contracts
        • Precompiled Contracts (Previous docs)
      • IDE and Tools
        • Truffle
      • Sample Contracts
        • KlaytnGreeter
        • ERC-20
          • 1. Writing ERC-20 Smart Contract
          • 2. Deploying Smart Contract
          • 3. Interacting with ERC-20 token from Klaytn Wallet
        • ERC-721
          • 1. Writing ERC-721 Smart Contract
          • 2. Deploying Smart Contract
      • Testing Guide
      • Deployment Guide
      • Klaytn Compatible Tokens
      • Porting Ethereum Contract
    • Run a Node
      • Deployment
        • Endpoint Node
          • System Requirements
          • Installation Guide
            • Download
            • Installation Guide
            • Configuration
            • Startup the EN
            • Testing the Installation
          • ken CLI commands
          • JSON-RPC APIs
        • Core Cell
          • System Requirements
          • Network Configuration
          • Installation Guide
            • Download
            • Before You Install
            • Consensus Node Setup
              • Installation Guide
              • Configuration
              • Startup the CN
            • Proxy Node Setup
              • Installation Guide
              • Configuration
              • Startup the PN
            • Testing the Core Cell
          • Monitoring Setup
          • H/A Setup
        • Service Chain
          • Getting Started
            • Setting up a 4-node Service Chain
            • Connecting to Baobab
            • Cross-Chain Value Transfer
            • HA(High Availability) for ServiceChain
            • Nested ServiceChain
            • Value Transfer between Sibling ServiceChains
          • Reference Manuals
            • System Requirements
            • Download
            • SCN User Guide
              • Installation
              • Configuration
              • Starting/Stopping SCN
              • Checking Node Status
              • kscn commands
              • homi commands
            • SPN/SEN User Guide
              • Installation
              • Configuration
              • Starting/Stopping Node
              • Checking Node Status
            • Bridge Configuration
            • Anchoring
            • KAS Anchoring
            • Value Transfer
            • Configuration Files
            • Log Files
            • Genesis JSON
            • Upgrade & Hard Fork
          • How-To Guides
        • Download Node Packages
          • v1.12.0
          • v1.11.1
          • v1.11.0
          • v1.10.2
          • v1.10.1
          • v1.10.0
          • v1.9.1
          • v1.9.0
          • v1.8.4
          • v1.8.3
          • v1.8.2
          • v1.8.1
          • v1.8.0
          • v1.7.3
          • v1.7.2
          • v1.7.1
          • v1.7.0
          • v1.6.4
          • v1.6.3
          • v1.6.2
          • v1.6.1
          • v1.6.0
          • v1.5.3
          • v1.5.2
          • v1.5.1
          • v1.5.0
          • v1.4.2
          • v1.4.1
          • v1.4.0
          • v1.3.0
          • v1.2.0
          • v1.1.1
          • v1.0.0
          • v0.9.6
          • v0.8.2
    • Operation Guide
      • Configuration
      • Node Log
      • Log operation
      • Errors & Troubleshooting
      • Klaytn Command
      • Chaindata Change
      • Chaindata Migration
    • dApp Developers
      • JSON-RPC APIs
        • API references
          • eth
            • Caution
            • Account
            • Block
            • Transaction
            • Config
            • Filter
            • Gas
            • Miscellaneous
          • klay
            • Account
            • Block
            • Transaction
              • Working with Klaytn Transaction Types
            • Configuration
            • Filter
            • Gas
            • Miscellaneous
          • net
          • debug
            • Logging
            • Profiling
            • Runtime Tracing
            • Runtime Debugging
            • VM Tracing
            • VM Standard Tracing
            • Blockchain Inspection
          • admin
          • personal
          • txpool
          • governance
        • Service Chain API references
          • mainbridge
          • subbridge
        • Transaction Error Codes
      • RPC Service Providers
        • Public Endpoints
      • SDK & Libraries for interacting with Klaytn Node
        • caver-js
          • Getting Started
          • Sending a sample transaction
          • API references
            • caver.account
            • caver.wallet
              • caver.wallet.keyring
            • caver.transaction
              • Basic
              • Fee Delegation
              • Partial Fee Delegation
            • caver.rpc
              • caver.rpc.klay
              • caver.rpc.net
              • caver.rpc.governance
            • caver.contract
            • caver.abi
            • caver.kct
              • caver.kct.kip7
              • caver.kct.kip17
              • caver.kct.kip37
            • caver.validator
            • caver.utils
            • caver.ipfs
          • caver-js ~v1.4.1
            • Getting Started (~v1.4.1)
            • API references
              • caver.klay
                • Account
                • Block
                • Transaction
                  • Legacy
                  • Value Transfer
                  • Value Transfer Memo
                  • Account Update
                  • Smart Contract Deploy
                  • Smart Contract Execution
                  • Cancel
                • Configuration
                • Filter
                • Miscellaneous
              • caver.klay.net
              • caver.klay.accounts
              • caver.klay.Contract
              • caver.klay.KIP7
              • caver.klay.KIP17
              • caver.klay.abi
              • caver.utils (~v1.4.1)
            • Porting from web3.js
        • caver-java
          • Getting Started
          • API references
          • caver-java ~v1.4.0
            • Getting Started (~v1.4.0)
            • Porting from web3j
        • ethers.js
        • web3.js
      • Tutorials
        • Klaytn Online Toolkit
        • Fee Delegation Example
        • Count DApp
          • 1. Environment Setup
          • 2. Clone Count DApp
          • 3. Directory Structure
          • 4. Write Smart Contract
          • 5. Frontend Code Overview
            • 5-1. Blocknumber Component
            • 5-2. Auth Component
            • 5-3. Count Component
          • 6. Deploy Contract
          • 7. Run App
        • Klaystagram
          • 1. Environment Setup
          • 2. Clone Klaystagram DApp
          • 3. Directory Structure
          • 4. Write Klaystagram Smart Contract
          • 5. Deploy Contract
          • 6. Frontend Code Overview
          • 7. FeedPage
            • 7-1. Connect Contract to Frontend
            • 7-2. UploadPhoto Component
            • 7-3. Feed Component
            • 7-4. TransferOwnership Component
          • 8. Run App
        • Building a Buy Me a Coffee dApp
          • 1. Project Setup
          • 2. Creating a BMC Smart Contract
          • 3. Testing the contract using scripts
          • 4. Deploying BMC Smart contract
          • 5. Building the BMC Frontend with React and Web3Onboard
          • 6. Deploying Frontend code on IPFS using Fleek
          • 7. Conclusion
        • Migrating Ethereum App to Klaytn
        • Connecting MetaMask
        • Connecting Remix
        • Verifying Smart Contracts Using Block Explorers
      • Developer Tools
        • Wallets
          • Kaikas
          • Klaytn Wallet
          • Klaytn Safe
            • Klaytn Safe Design
            • Create a Safe
            • Add assets
            • Send assets
            • Contract Interaction
            • Transaction Builder
            • Points to Note
            • Frequently Asked Questions
          • SafePal S1
          • Wallet Libraries
            • Web3Auth
            • Web3Modal
            • Web3-Onboard
            • Particle Network
        • Oracles
          • Orakl Network
          • Witnet
          • SupraOracles
        • Indexers
          • SubQuery
        • Cross-chain
          • LayerZero
        • Block Explorers
          • Klaytnscope
          • Klaytnfinder
        • Klaytn Contracts Wizard
    • Glossary
  • ---
    • Klaytn Hard Fork History
    • Klaytn 2.0
      • Metaverse Package
      • Finality and Improvements
      • Ethereum Compatibility
      • Decentralizing Governance
      • Massive Eco Fund
    • FAQ
    • Open Source
    • Terms of Use
    • Languages
  • ℹ️Latest Klaytn Docs
Powered by GitBook
On this page
  • introduction
  • Prerequisites
  • Setup Project
  • Install web3.js
  • Initialize web3.js
  • Reading data from the blockchain
  • Sending transaction to the blockchain
  • Interact with smart contracts
  1. -
  2. dApp Developers
  3. SDK & Libraries for interacting with Klaytn Node

web3.js

Previousethers.jsNextTutorials

Last updated 1 year ago

introduction

is a JavaScript library that allows developers to interact with EVM-compatible blockchain networks like Klaytn. With Klaytn supporting features for , Ethereum tools such as web3.js can be used on Klaytn without any significant modifications.

Thus, developers can leverage this compatibility and use the web3.js library to interact with a Klaytn node.

In this guide, you'll learn how to use the web3.js library to send a transaction, read data from the blockchain and interact with an existing contract on the Klaytn Network.

Prerequisites

Setup Project

To get started, you need to create a project directory to house the files to be created in this guide.

mkdir web3-js
cd web3-js

Install web3.js

To install web3.js run the following command in your terminal:

npm install web3

Initialize web3.js

In this tutorial, we would be creating a bunch of scripts file to send transactions, read data from the blockchain, and also interact with existing smart contract. To get started, you need to know how to initialize web3.js for each of your script files.

Import web3 into your script file.

const { Web3 } = require('web3');

After successfully importing web3, you need to connect to Klaytn by instantiating a new web3.js object with an RPC URL of the Klaytn network. Add the code below to the existing code:

const url = "RPC URL"  
const web3 = new Web3(url);

Further, you need to add your private key to sign transactions. Add the code below to the existing code:

const privateKey = "Paste private key";

Reading data from the blockchain

To read data from the blockchain, create a new read.js file in your project folder by running this command:

touch read.js

After creating this file, initialize web3 as done in the initialize section. In this section, you'll learn how to read data from the blockchain (e.g., blockNumber, KLAY balance).

To see this in action, paste the following code in your read.js.

const { Web3 } = require('web3');

const url = "RPC URL"
const web3 = new Web3(url);

async function getLatestBlock() {
    const latestBlock = await web3.eth.getBlockNumber();
    console.log(latestBlock.toString());
}

async function getKlayBalance() {
    const klayBalance  = await web3.eth.getBalance("Paste wallet address");
    const formatBalance = await web3.utils.fromWei(klayBalance, 'ether');
    console.log(`You have ${formatBalance} KLAY`);
}

// call the following functions
getLatestBlock();
getKlayBalance();

Output

To run the script and read data from the blockchain, you can run the following command in your terminal:

node read.js

If the transaction was succesful, you'll see the block number and user’s KLAY balance been logged in your terminal.

Sending transaction to the blockchain

To send transaction to the blockchain, create a new send.js file in your project folder by running this command:

touch send.js

After creating this file, initialize web3 as done in the initialize section. In this section, you ll learn how to send transaction to the blockchain e.g send KLAY to an address.

To see this in action, paste the following code in your send.js.

const { Web3 } = require('web3');

const url = "RPC URL";
const web3 = new Web3(url);

const senderPrivateKey = "Paste private key";
const senderAddr = "Paste sender address";
const recipientAddr = "Paste recipient address";

async function sendTx() {
    const tx = await web3.eth.accounts.signTransaction({
        from: senderAddr,
        to: recipientAddr,
        value: 90000000000,
        maxFeePerGas: 250000000000,
        maxPriorityFeePerGas: 250000000000,
        gas: 21000,
    }, privateKey);

    const receipt = await web3.eth.sendSignedTransaction(tx.rawTransaction);
    console.log(receipt);
}

// call function
sendTx();

Output

To run the script and send data to the blockchain, you can run the following command in your terminal:

node send.js

If the transaction was succesful, you'll see the transaction receipt been logged in your terminal.

Interact with smart contracts

To interact with an existing smart contract on Klaytn, create a new interact.js file in your project folder by running this command:

touch interact.js

After creating this file, initialize web3 as done in the initialize section. In this section, you will use web3.js to interact with a smart contract on Klaytn by instantiating a Contract object using the ABI and address of a deployed contract.

To see this in action, paste the following code in your interact.js.

const { Web3 } = require('web3');

const url = "RPC URL"  
const web3 = new Web3(url);

const privateKey = "Paste private key";

// replace with your contract ABI
const abi = [
    {
        "inputs": [],
        "name": "retrieve",
        "outputs": [
            {
                "internalType": "uint256",
                "name": "",
                "type": "uint256"
            }
        ],
        "stateMutability": "view",
        "type": "function"
    },
    {
        "inputs": [
            {
                "internalType": "uint256",
                "name": "num",
                "type": "uint256"
            }
        ],
        "name": "store",
        "outputs": [],
        "stateMutability": "nonpayable",
        "type": "function"
    }
]
    
    // replace with your contract address
    const contractAddress = "0x472a1226796b6a0918DC78d40b87d750881fdbDC"
    
    const contract = new web3.eth.Contract(abi, contractAddress);
    
    // Can replace `10` with any value you want to store
    const storeTx = contract.methods.store(10);
    
    // send transaction to smart contract
    // modify contract
    async function setValue() {
        
     // Sign Tx with private key
    const createTransaction = await web3.eth.accounts.signTransaction(
        {
          to: contractAddress,
          data: storeTx.encodeABI(),
          gas: await storeTx.estimateGas(),
          maxFeePerGas: 250000000000,
          maxPriorityFeePerGas: 250000000000,
        },
        privateKey
      );
    
      // Send Tx and Wait for Receipt
      const createReceipt = await web3.eth.sendSignedTransaction(createTransaction.rawTransaction);
      console.log(`Tx hash: ${createReceipt.transactionHash}`);

      }

      // read contract data
      async function retrieveValue() {
        // read from contract
        const tx = await contract.methods.retrieve().call();
        console.log(tx);
      }
      
      // call functions
      setValue();
      retrieveValue();

Output

To run the script and interact with smart contracts, you can run the following command in your terminal:

node interact.js

If the transaction was succesful, in your terminal you'll see the transaction hash and the value stored.

Code-Editor: a source-code editor such as .

: used to deploy the contracts, sign transactions and interact with the contracts.

RPC Endpoint: you can get this from one of the supported .

Test KLAY from : fund your account with sufficient KLAY.

For the purpose of this guide, a simple_storage contract was compiled and deployed on . We will be sending a transaction to the contract by calling the store function and also reading from it by calling the retrieve function.

For more in-depth guide on web3.js, please refer to . Also, you can find the full implementation of the code for this guide on

VS-Code
Metamask
Endpoint Providers
Faucet
NodeJS and NPM
Remix IDE
web3.js docs
GitHub
web3.js
Ethereum Equivalence