Smart Contract Execution using Fee Delegation (sender has no KLAY)

fee_delegated_execution.js

const Caver = require('caver-js');
const caver = new Caver('https://api.baobab.klaytn.net:8651/');

caver.klay.accounts.wallet.create(1);
const sender = caver.klay.accounts.wallet[0];
// if there is only one key bound to an address where last160bits(keccak(key)) === address, then the key can function as payer key
const payer = caver.klay.accounts.wallet.add('0x42605fa83957d67ca8e5c843820c72037ee5dbc6b0b2d14f9d4bd5de41b446de');

// an arbitrary contract is used
async function run() {
    caver.klay.getAccount(sender.address).then(console.log); // should print `null`

    // make sure `data` starts with 0x
    const { rawTransaction: senderRawTransaction } = await caver.klay.accounts.signTransaction({
        type: 'FEE_DELEGATED_SMART_CONTRACT_EXECUTION',
        from: sender.address,
        data: "some_data_represented_in_hex",
        gas: '3000000',
        value: 0,
    }, sender.privateKey);

    // signed raw transaction
    console.log("Raw TX:\n", senderRawTransaction);
    
    // send fee delegated transaction with fee payer information
    caver.klay.sendTransaction({
        senderRawTransaction: senderRawTransaction,
        feePayer: payer.address
    })
        .on('transactionHash', function (hash) {
            console.log(">>> tx_hash for deploy =", hash);
        })
        .on('receipt', function (receipt) {
            console.log(">>> receipt arrived: ", receipt);
            
            caver.klay.getAccount(sender.address).then(console.log); // should NOT print `null`
        })
        .on('error', function (err) {
            console.error(">>> error: ", err);
        });
}

run();