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无气

从**@kaiachain/web3js-ext软件包导入Web3**，在 web3js 上添加无气体功能

ERC20 令牌地址（Kairos 测试网上的 TEST 令牌）。

声明 senderAddr: 执行交换的发送方的钱包地址，以及 senderPriv: 发送方用于签署交易的私钥。

使用 Kaia Kairos 测试网创建 JSON-RPC 提供程序和 Wallet 实例

从 ** 发件人私钥 ** 声明 ** 发件人账户 **

ERC20 令牌的最小 ABI，包括查询小数、符号、津贴和余额的功能。

发送方希望从掉期中获得的 0.01 KAIA（单位：魏）的固定金额，用于为后续申请交易提供资金。

在地址处显示令牌：

创建一个 ERC20 令牌合约实例，以便与其功能交互。

查询令牌的符号（例如，"TEST "表示 TEST 令牌）。

查询代币的小数位数（如 ETH 或 TEST 等大多数 ERC20 代币的小数位数为 18）。

查询发送方的 ERC20 令牌余额。

显示发件人的初始余额。

读取 GaslessSwapRouter 合约的实例，该合约可促进 Kaia 区块链上的无气体代币交换。

读取 GaslessSwapRouter 合约的区块链地址。

检查 GaslessSwapRouter 是否支持指定的 ERC20 令牌进行无气体交换。

读取 GaslessSwapRouter 为促进无气体交换而收取的佣金率。

显示 GaslessSwapRouter 地址、true（如果支持令牌）和佣金率。

检查允许 GaslessSwapRouter 代表发送方使用多少令牌。

通过检查备付金是否为零，确定是否需要进行审批交易。

初始化一个空数组，用于存储稍后发送的事务。

根据 approveRequired 标志检查是否需要进行审批交易。 生成 ERC20 批准交易，允许 GaslessSwapRouter 使用发送方的代币。

从区块链中读取当前天然气价格，并将其转换为 JavaScript 数字。

计算发送者必须偿还给区块矿工的 KAIA 总金额（单位：微元），以支付交易的气体成本。

计算掉期必须产生的最低 KAIA 金额（单位：魏），以支付还款、佣金和所需的申请交易费。

计算要交换的 ERC20 代币数量，以至少收到 minAmountOut KAIA，同时考虑滑点。

检查发送方的 ERC20 代币余额是否不足以支付交换所需的代币数量。

生成交换交易，用指定数量的 ERC20 代币交换至少最低数量的 KAIA，并结合无气体还款逻辑。 将交换事务添加到 txs 数组，以便批量执行。

使用发送者的钱包发送 txs 数组中的所有交易。 遍历发送的事务，记录其详细信息。

向区块链发送已签名交易数组，并等待其交易收据。

列出与发件人有关的区块交易

寄件人的最终余额

Gasless.js

const { Web3 } = require("@kaiachain/web3js-ext");

// Replace with ERC20 token address to be spent

const tokenAddr = "0xcB00BA2cAb67A3771f9ca1Fa48FDa8881B457750"; // Kairos:TEST token

// Replace with your wallet address and private key

const senderAddr = "0x24e8efd18d65bcb6b3ba15a4698c0b0d69d13ff7";

const senderPriv = "0x4a72b3d09c3d5e28e8652e0111f9c4ce252e8299aad95bb219a38eb0a3f4da49";

const provider = new Web3.providers.HttpProvider("https://public-en-kairos.node.kaia.io");

const web3 = new Web3(provider);

const senderAccount = web3.eth.accounts.privateKeyToAccount(senderPriv);

const ERC20_ABI = JSON.parse('[{"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"symbol","outputs":[{"internalType":"string","name":"","type":"string"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"decimals","outputs":[{"internalType":"uint8","name":"","type":"uint8"}],"stateMutability":"view","type":"function"},{"inputs":[],"name":"totalSupply","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"account","type":"address"}],"name":"balanceOf","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"address","name":"recipient","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transfer","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"sender","type":"address"},{"internalType":"address","name":"recipient","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"transferFrom","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"spender","type":"address"},{"internalType":"uint256","name":"amount","type":"uint256"}],"name":"approve","outputs":[{"internalType":"bool","name":"","type":"bool"}],"stateMutability":"nonpayable","type":"function"},{"inputs":[{"internalType":"address","name":"owner","type":"address"},{"internalType":"address","name":"spender","type":"address"}],"name":"allowance","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":false,"internalType":"uint256","name":"value","type":"uint256"}],"name":"Transfer","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"owner","type":"address"},{"indexed":true,"internalType":"address","name":"spender","type":"address"},{"indexed":false,"internalType":"uint256","name":"value","type":"uint256"}],"name":"Approval","type":"event"}]');

// senderAddr wants to swap the ERC20 token for at least 0.01 KAIA so she can execute the AppTx.

async function main() {

const appTxFee = web3.utils.toWei("0.01", "ether");

console.log(`Using token at address: ${tokenAddr}`);

const token = new web3.eth.Contract(ERC20_ABI, tokenAddr);

const tokenSymbol = await token.methods.symbol().call();

const tokenDecimals = parseInt(await token.methods.decimals().call());

const tokenBalance = await token.methods.balanceOf(senderAddr).call();

console.log(`\nInitial balance of the sender ${senderAddr}`);

console.log(`- ${web3.utils.fromWei(await web3.eth.getBalance(senderAddr), "ether")} KAIA`);

console.log(`- ${web3.utils.fromWei(tokenBalance, tokenDecimals)} ${tokenSymbol}`);

const router = await web3.gasless.getGaslessSwapRouter();

const routerAddr = await router.options.address;

const isTokenSupported = await router.methods.isTokenSupported(tokenAddr).call();

const commissionRate = await router.methods.commissionRate().call();

console.log(`\nGaslessSwapRouter address: ${routerAddr}`);

console.log(`- The token is supported: ${isTokenSupported}`);

console.log(`- Commission rate: ${commissionRate} bps`);

// If sender hasn't approved, include ApproveTx first.

const allowance = await token.methods.allowance(senderAddr, routerAddr).call();

const approveRequired = (allowance == 0n);

const txs = [];

if (approveRequired) {

console.log("\nAdding ApproveTx because allowance is 0");

const approveTx = await web3.gasless.getApproveTx(

senderAddr,

tokenAddr,

routerAddr,

gasPrice,

);

txs.push(approveTx);

} else {

console.log("\nNo ApproveTx needed");

}

// - amountRepay (KAIA) is the cost of LendTx, ApproveTx, and SwapTx. The block miner shall fund it first,

// then the sender has to repay from the swap output.

// - minAmountOut (KAIA) is the required amount of the swap output. It must be enough to cover the amountRepay

// and pay the commission, still leaving appTxFee.

// - amountIn (token) is the amount of the token to be swapped to produce minAmountOut plus slippage.

console.log(`\nCalculating the amount of the token to be swapped...`);

const gasPrice = await web3.eth.getGasPrice();

console.log(`- gasPrice: ${web3.utils.fromWei(gasPrice, "gwei")} gkei`);

const amountRepay = web3.gasless.getAmountRepay(approveRequired, gasPrice);

console.log(`- amountRepay: ${web3.utils.fromWei(amountRepay, "ether")} KAIA`);

const minAmountOut = web3.gasless.getMinAmountOut(amountRepay, appTxFee, commissionRate);

console.log(`- minAmountOut: ${web3.utils.fromWei(minAmountOut, "ether")} KAIA`);

const slippageBps = 50 // 0.5%

const amountIn = await web3.gasless.getAmountIn(router, tokenAddr, minAmountOut, slippageBps);

console.log(`- amountIn: ${web3.utils.fromWei(amountIn, tokenDecimals)} ${tokenSymbol}`);

if (tokenBalance < amountIn) {

console.log(`\nInsufficient balance of the token: ${web3.utils.fromWei(tokenBalance, tokenDecimals)} ${tokenSymbol}`);

console.log(`- Please transfer more ${tokenSymbol} to the sender ${senderAddr}`);

return;

}

const swapTx = await web3.gasless.getSwapTx(

senderAddr,

tokenAddr,

routerAddr,

amountIn,

minAmountOut,

amountRepay,

gasPrice,

approveRequired,

);

txs.push(swapTx);

console.log("\nSending transactions and waiting for them to be mined...");

const signedTxs = [];

const txHashes = []

for (const tx of txs) {

const signResult = await senderAccount.signTransaction(tx);

signedTxs.push(signResult.rawTransaction);

txHashes.push(signResult.transactionHash);

console.log(`- Tx signed: (nonce: ${tx.nonce}) ${signResult.transactionHash} ${signResult.rawTransaction}`);

}

const receipts = await web3.eth.sendSignedTransactions(signedTxs);

console.log("\nListing the block's transactions related to the sender...");

const block = await web3.eth.getBlock(receipts[0].blockNumber);

const names = {

[senderAddr.toLowerCase()]: "sender",

[tokenAddr.toLowerCase()]: "token",

[routerAddr.toLowerCase()]: "router",

}

for (const txhash of block.transactions) {

const tx = await web3.eth.getTransaction(txhash);

const fromName = names[tx.from.toLowerCase()] || tx.from;

const toName = names[tx.to.toLowerCase()] || tx.to;

if (fromName != tx.from || toName != tx.to) {

console.log(`- Tx ${tx.hash}: ${fromName} => ${toName}`);

}

}

console.log(`\nFinal balance of the sender ${senderAddr}`);

console.log(`- ${web3.utils.fromWei(await web3.eth.getBalance(senderAddr), "ether")} KAIA`);

console.log(`- ${web3.utils.fromWei(await token.methods.balanceOf(senderAddr).call(), tokenDecimals)} ${tokenSymbol}`);

}

main();

output

❯ node Gasless.js

Using token at address: 0xcB00BA2cAb67A3771f9ca1Fa48FDa8881B457750

Initial balance of the sender 0x24e8efd18d65bcb6b3ba15a4698c0b0d69d13ff7

- 49.9969537425 KAIA

- 3.0 TEST

GaslessSwapRouter address: 0x4b41783732810b731569E4d944F59372F411BEa2

- The token is supported: true

- Commission rate: 0 bps

- 3.0 TEST

GaslessSwapRouter address: 0x4b41783732810b731569E4d944F59372F411BEa2

- The token is supported: true

- Commission rate: 0 bps

GaslessSwapRouter address: 0x4b41783732810b731569E4d944F59372F411BEa2

- The token is supported: true

- Commission rate: 0 bps

- The token is supported: true

- Commission rate: 0 bps

- Commission rate: 0 bps

Adding ApproveTx because allowance is 0

Calculating the amount of the token to be swapped...

- gasPrice: 27.5 gkei

- amountRepay: 0.0170775 KAIA

- minAmountOut: 0.0270775 KAIA

- amountIn: 0.027300931296609197 TEST

Sending transactions and waiting for them to be mined...

- Tx signed: (nonce: 5) 0x1d2bd9e5ae11653b8cddb297d040074b189fe456ae986197c4c2bbf74a51e6ef

- Tx signed: (nonce: 6) 0x96dd81962d7ae14baf31bd0a8afb900be1a6c9c8d30ad854011a4120fb0efbaf

Listing the block's transactions related to the sender...

- Tx 0x50769b14c7814f4e6b169f63595c1c19d9c46ce1c626c14b6b3c5610f691f58a: 0xB74Ff9DEa397fE9E231df545eb53fE2ADF776cb2 => sender

- Tx 0x1d2bd9e5ae11653b8cddb297d040074b189fe456ae986197c4c2bbf74a51e6ef: sender => token

- Tx 0x96dd81962d7ae14baf31bd0a8afb900be1a6c9c8d30ad854011a4120fb0efbaf: sender => router

Final balance of the sender 0x24e8efd18d65bcb6b3ba15a4698c0b0d69d13ff7

- 50.016275725 KAIA

- 2.972699068703390803 TEST