監聽與過濾

過濾

尋找過去特定的 Event
利用 Ethers v6 的 .queryFilter

contract.queryFilter(contract.filters.Transfer(null, null),fromblock,toblock);

第一欄放 Event 名稱與指定的參數，第二欄放區塊起始，第三欄放區塊終止，需要注意的是 ALCHEMY API 的搜尋區塊範圍只有 10 個區塊。

require('dotenv').config();
const { ethers } = require("hardhat");

const provider = new ethers.JsonRpcProvider(`https://eth-mainnet.g.alchemy.com/v2/${process.env.ALCHEMY_API_KEY}`);
const contractaddr = "0xdAC17F958D2ee523a2206206994597C13D831ec7";
const contractABI = ["event Transfer(address indexed from, address indexed to, uint256 value)"];
const fromblock = 24230331
const toblock = 24230332

async function main(){
		//作法1
    const contract = new ethers.Contract(contractaddr,contractABI,provider);
    const log = await contract.queryFilter(contract.filters.Transfer(null, null),fromblock,toblock);
    // const log = await contract.queryFilter("Transfer",fromblock,toblock)
    console.log("From:", log[0].args[0], "To:", log[0].args[1], "Value:", Number(log[0].args[2]/1000000n));
    console.log(log[0]);
		
		//作法2
    const iface = new ethers.Interface(contractABI);
    const from = "0x3C02290922a3618A4646E3BbCa65853eA45FE7C6";
    const to = "0xFAdEf4c677C2f31F43f09e239b34D0F6905a3085"
    const filter = {
    address: contractaddr,
    topics: [
        iface.getEvent("Transfer").topicHash, 
        ethers.zeroPadValue(from, 32),
        ethers.zeroPadValue(to, 32),
    ],
        fromBlock: fromblock,
        toBlock: toblock
    };

    const log = await provider.getLogs(filter);
    console.log(log[0]);
    console.log(Number(log[0].data) / 1e6);

}
main().catch(console.error);   

監聽

即時監聽鏈上事件

async function listen() {
    const provider = new ethers.WebSocketProvider(`https://eth-mainnet.g.alchemy.com/v2/${process.env.ALCHEMY_API_KEY}`);
    const contract = new ethers.Contract(contractaddr,contractABI,provider);
    contract.once('Transfer', (from, to, value, event) => {
    console.log({
      from,
      to,
      value: ethers.formatUnits(value, 6), 
      blockNumber: event.log.blockNumber,
      txHash: event.log.transactionHash
    });
  });

}
listen().catch(console.error)