前言

延续《快速实现一个闪电贷智能合约》，这一篇直切“前端交互”。
我们把「编译→部署→事件监听→异常捕获→Gas 估算→余额刷新」等必踩深坑，压缩成 3 个可一键复现的用户故事：

1. 正常借 100 ETH，15 秒内连本带息归还；
2. 部署“老赖”合约，故意不还，亲眼看交易被 revert；
3. 极限测试：输入 0 或一次性借空池子，验证防御逻辑。

前期准备

• hardhat启动网络节点：npx hardhat node
• 合约编译：npx hardhat compile 生成对应的xxx.json用获取abi等相关信息
• 合约部署：npx hardhat deploy --tags token,FlashLoan,FlashLoanReceiver 获取合约地址(代币、借贷和借贷接收合约地址)
• 节点的私钥导入钱包：用来与合约交互时支付对应的gas费

恶意接收者合约

说明：为测试借款不还场景，编写的合约包含编译、部署

恶意不还款者合约

• 合约

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC20/IERC20.sol";

contract FlashLoanReceiver1 {
    // 闪电贷回调函数
    function executeOperation(
        address asset,
        uint256 amount,
        uint256 premium,
        address initiator,
        bytes calldata params
    ) external returns (bool) {
        // 在这里执行闪电贷逻辑
        
        // 还款
        // uint256 amountToRepay = amount + premium;
        // IERC20(asset).transfer(msg.sender, amountToRepay);
        
        return true;
    }
}

• 部署脚本

module.exports = async function ({getNamedAccounts,deployments}) {
    const firstAccount = (await getNamedAccounts()).firstAccount;
    const {deploy,log} = deployments;
    const FlashLoanReceiver1=await deploy("FlashLoanReceiver1",{
        contract: "FlashLoanReceiver1",
        from: firstAccount,
        args: [],//参数 owner
        log: true,
        // waitConfirmations: 1,
    })
    console.log("FlashLoanReceiver1合约地址 恶意不还款接收者",FlashLoanReceiver1.address)
  }
  module.exports.tags = ["all", "FlashLoanReceiver1"]

• 相关指令
  • 编译：npx hardhat compile
  • 部署： npx hardhat deploy --tags FlashLoanReceiver1

前端代码（核心）

代码公共部分

import { abi as FlashLoanABI } from '@/abi/FlashLoan.json';
import { abi as FlashLoanReceiverABI } from '@/abi/FlashLoanReceiver.json';
import { abi as FlashLoanReceiver1ABI } from '@/abi/FlashLoanReceiver1.json';
import { abi as MyTokenABI } from '@/abi/MyToken.json';
import * as ethers from 'ethers';

场景1（正常借贷流程）

const FlashLoanFn= async()=>{
        const provider = new ethers.providers.Web3Provider(window.ethereum);
        await provider.send('eth_requestAccounts', []); // 唤起钱包
        const signer = await provider.getSigner();
        const FlashLoanAddress="0x7a2088a1bFc9d81c55368AE168C2C02570cB814F"
        const FlashLoanReceiverAddress="0x09635F643e140090A9A8Dcd712eD6285858ceBef"
        const MyTokenAddress="0x5FbDB2315678afecb367f032d93F642f64180aa3"
        const FlashLoanContract = new ethers.Contract(FlashLoanAddress, FlashLoanABI, signer);
        const FlashLoanReceiverContract = new ethers.Contract(FlashLoanReceiverAddress, FlashLoanReceiverABI, signer);
        const MyTokenContract = new ethers.Contract(MyTokenAddress, MyTokenABI, signer);
        
        console.log("完成借贷池子中的余额前",ethers.utils.formatEther(await MyTokenContract.balanceOf(FlashLoanAddress)))
          const loanAmount = ethers.utils.parseEther("100");          // 100 ether
            const fee = (loanAmount.mul(5)).div(10000);//0.05%手续费
            console.log("loanAmount :", ethers.utils.formatEther(loanAmount), "ETH");
  console.log("fee       :", ethers.utils.formatEther(fee), "ETH");
  /* ---------- 1. 给接收者转手续费 ---------- */
  const tx1 = await MyTokenContract.transfer(FlashLoanReceiverAddress, fee);
  await tx1.wait();

  /* ---------- 2. 执行闪电贷 ---------- */
  const tx2 = await FlashLoanContract.flashLoan(
    FlashLoanReceiverAddress,
    MyTokenAddress,
    loanAmount,
    "0x"
  );

  /* ---------- 3. 等待事件 ---------- */
  const receipt = await tx2.wait();
  const event = receipt.events?.find((e: any) => e.event === "FlashLoan");
  console.log("完成借贷池子中的余额",ethers.utils.formatEther(await MyTokenContract.balanceOf(FlashLoanAddress)))
  if (!event) throw new Error("FlashLoan 事件未触发");

  console.log("✅ FlashLoan 事件参数:", event.args);

场景2（恶意借款不还）

 const FlashLoanFn=async ()=>{
        const provider = new ethers.providers.Web3Provider(window.ethereum);
        await provider.send('eth_requestAccounts', []); // 唤起钱包
        const signer = await provider.getSigner();
        const FlashLoanAddress="0x7a2088a1bFc9d81c55368AE168C2C02570cB814F"
        const FlashLoanReceiverAddress="0x09635F643e140090A9A8Dcd712eD6285858ceBef"
        const FlashLoanReceiver1Address="0xc5a5C42992dECbae36851359345FE25997F5C42d"//恶意不还款
        const MyTokenAddress="0x5FbDB2315678afecb367f032d93F642f64180aa3"
        const FlashLoanContract = new ethers.Contract(FlashLoanAddress, FlashLoanABI, signer);
        const FlashLoanReceiverContract = new ethers.Contract(FlashLoanReceiverAddress, FlashLoanReceiverABI, signer);
//池子中有余额
        await MyTokenContract.mint(
                FlashLoanAddress,
                ethers.utils.parseEther("1000")
            );
        console.log("前----",ethers.utils.formatEther(await MyTokenContract.balanceOf(FlashLoanAddress)))
          const loanAmount = ethers.utils.parseEther("100");          // 100 ether
            const fee = (loanAmount.mul(5)).div(10000);//0.05%手续费
            console.log("loanAmount :", ethers.utils.formatEther(loanAmount), "ETH");
  console.log("fee       :", ethers.utils.formatEther(fee), "ETH");
  /* ---------- 1. 给接收者转手续费 ---------- */
  try {
    // 池子余额已充足，但接收者不会还款 → 预期 revert
    const tx = await FlashLoanContract.flashLoan(
      FlashLoanReceiver1Address,
      MyTokenAddress,
      ethers.utils.parseEther("100"),
      "0x"
    );
    await tx.wait();          // 如果走到这里，说明测试失败
    alert("❌ 交易居然成功了，接收者应该还钱才对！");
  } catch (err: any) {
    // 捕获 revert 字符串
    const reason = err.reason || err.message || "";
    if (reason.includes("Flash loan not repaid")) {
      alert("✅ 闪电贷成功 revert：贷款未偿还（符合预期）");
    } else {
      alert("⛔ 其他错误：" + reason);
    }
  }
    }

场景3（正常闪电贷的边界处理）

• 无借贷（金额为0）

# 核心代码
const tx = await FlashLoanContract.flashLoan(
    FlashLoanReceiver1Address,
    MyTokenAddress,
    0,//借款为0
    "0x"
  );

• 池子中余额不足

# 核心代码
const hugeAmount = ethers.parseEther("10000");
 const tx = await FlashLoanContract.flashLoan(
    FlashLoanReceiver1Address,
    MyTokenAddress,
    hugeAmount,//超过池中的款项
    "0x"
  );

效果图

<div style="display:flex; gap:8px;flex-wrap:wrap;"> <img src="https://p0-xtjj-private.juejin.cn/tos-cn-i-73owjymdk6/01128c5a5b6043f0bda38817bc851258tplv-73owjymdk6-jj-mark-v1:0:0:0:0:5o6Y6YeR5oqA5pyv56S-5Yy6IEAg5pyo6KW_:q75.awebp?policy=eyJ2bSI6MywidWlkIjoiMjQzNjE3MzQ5Njg0NTU0OSJ9&rk3s=e9ecf3d6&x-orig-authkey=f32326d3454f2ac7e96d3d06cdbb035152127018&x-orig-expires=1757668998&x-orig-sign=hHmD%2FG2MtcIsmKEf9CDTHZaaaRA%3D" alt="图1转存失败，建议直接上传图片文件" width="200"> <img src="https://p0-xtjj-private.juejin.cn/tos-cn-i-73owjymdk6/601501aa839c42bfacd2ed99e6cf510dtplv-73owjymdk6-jj-mark-v1:0:0:0:0:5o6Y6YeR5oqA5pyv56S-5Yy6IEAg5pyo6KW_:q75.awebp?policy=eyJ2bSI6MywidWlkIjoiMjQzNjE3MzQ5Njg0NTU0OSJ9&rk3s=e9ecf3d6&x-orig-authkey=f32326d3454f2ac7e96d3d06cdbb035152127018&x-orig-expires=1757668946&x-orig-sign=YbBCtr5%2FbIydJiDQQkD%2BFYvxRI4%3D" alt="图1转存失败，建议直接上传图片文件" width="200"> </div>

总结

文章用“三段式”代码把闪电贷的前端交互拆成乐高：

• 准备阶段：Hardhat 本地链 + 合约编译部署脚本一次性启动，私钥导入 MetaMask 即可秒出 10 个富裕账户；
• 场景阶段：
  – 正常流程演示了“先转手续费 → 发起 flashLoan → 监听事件 → 余额校验”完整闭环；
  – 恶意接收者把还款逻辑注释掉，前端立刻捕获 revert，并解析 reason 字符串，让“不还钱就 revert”变得肉眼可见；
  – 边界测试用 0 借款与超额借款两条用例，验证合约的 defensive 逻辑，同时展示 ethers 抛错与 revert reason 的抓取技巧。
• 交付物：三段可复制的 React/Vanilla 函数、四张效果截图、一条“console 即审计”的体验路径。

后续优化，也可以把池子换成 Aave、把代币换成 DAI，就能把同样的代码直接搬到主网 Fork 上继续“闪电”。