caver-js is a JavaScript API library that allows developers to interact with a Klaytn node using a HTTP or Websocket connection. It is available on npm.


  • HTTP 및 웹소켓을 통한 Klaytn의 JSON-RPC 클라이언트 API의 완전한 구현
  • Support of Klaytn transaction, account, and account key types
  • Klaytn 네트워크에서 스마트 컨트랙트를 배포하고 실행하기위한 자바스크립트 스마트 컨트랙트 패키지
  • Klaytn 계정 관리를 위한 인메모리 지갑
  • 수수료 위임 지원
  • Klaytn Wallet 키 형식 지원
  • RLP에서 트랜잭션 오브젝트의 인코딩/디코딩
  • 트랜잭션 객체의 서명
  • web3-js 애플리케이션을 caver-js로 쉽게 포팅

caver-js의 패키지

Below are packages provided in caver-js.

오류 코드 개선

The error messages from Ethereum via web3.js are hardly figuring out where the error occurs. caver-js improves the interface to catch error messages from Klaytn.
More details can be found in the value of txError of the transaction receipt like the below:
Error: runtime error occurred in interpreter
"blockHash": "0xe7ec35c9fff1178d52cee1d46d40627d19f828c4b06ad1a5c3807698b99acb20",
"blockNumber": 7811,
"contractAddress": null,
"from": "0xa8a2d37727197cc0eb827f8c5a3a3aceb26cf59e",
"gasUsed": 9900000000,
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
"status": false,
"to": "0xf8425b0f65147969621f9390ca06139c7b439497",
"transactionHash": "0x85ce2b307899c90144442d9b3236827ac57375c522be2435093aebfd920b8c58",
"transactionIndex": 0,
"txError": "0x2",
"events": {}

Klaytn에 트랜잭션을 보낼 때 주의사항

Klaytn has a new gas price policy since the Magma hard fork which enabled the KIP-71.
Therefore, you need to set the gasPrice logic differently when sending a transaction, depending on whether the hard fork is applicable or not.
Until the Magma hard fork, transactions on Klaytn have been subject to a "fixed gas price". Therefore, transactions with any other price submitted to the network are rejected. If gasPrice is not defined when you sign or submit a transaction, caver-js uses caver.rpc.klay.getGasPrice RPC call to set the gas price.
After the Magma hard fork, Klaytn uses a "dynamic gas fee pricing mechanism". The gas price of the transaction should be higher than the base fee of the Klaytn network. If gasPrice is not defined when you sign or submit a transaction, caver-js sets the gasPrice field of the transaction using caver.rpc.klay.getGasPrice.

How to set gasPrice field

caver-js provides various ways to set the gasPrice. Ways to set the gasPrice field when using caver-js are suggested below. The methods described here can be used regardless of the hard fork.

Do not define gasPrice field

If you create an instance without defining the gasPrice field, the gasPrice field is automatically set when you call tx.sign or tx.signAsFeePayer to sign a transaction.
const tx = caver.transaction.valueTransfer.create({ from, to, value, gas })
await tx.sign(from, tx) // Before signing, gasPrice is set inside `tx.sign`.

Use tx.fillTransaction method

You can use tx.fillTransaction, a function that fills the optional fields of a transaction with appropriate values when they are omitted.
const tx = caver.transaction.valueTransfer.create({ from, to, value, gas })
await tx.fillTransaction() // Fill the optional tx fields.

Use tx.suggestGasPrice method

You can set the gasPrice with the result of tx.suggestGasPrice which returns the recommended gas price.
const tx = caver.transaction.valueTransfer.create({ from, to, value, gas })
tx.gasPrice = await tx.suggestGasPrice()
For more information about the gas price, see Gas and Unit Price Overview The price of gas used in the network can be obtained by using caver.rpc.klay.getGasPrice.