web3.js 常见用法

常见web3对象用法示例：

 /// 创建 web3 对象实例
 var Web3 = require("web3")
 var web3 = new Web3()
 web3.setProvider("http://localhost:8545")
 /// --- web3.eth
 /// 转账
 web3.eth.sendTransaction({
     from: '0x65290c7c646F050F2f80387B7cd33fD10c409bE0',
     to: '0x16E89d23411F37C4e0374B1810C1438DD9Aa87b1',
     value: '1000000000000000000'
 },function(error, hash){
     console.log(error,hash)
 })
 /// --- web3.eth.Contract
 /// 调用合约
 var contractJson = require("./build/contracts/Demo.json");
 var abi = contractJson.abi;
 var contractAddress = '0x6CDb1a024d6EA0CB976f61f9d746907B984fd7b4'
 var myContract = new web3.eth.Contract(abi, contractAddress, {
     from: '0x65290c7c646F050F2f80387B7cd33fD10c409bE0',
     gasPrice: '20000000000'
 })
 // 调用合约方法: add
 myContract.methods.add(2).send({}, function(error, transactionHash){
     console.log(error,transactionHash)
 })
 // 调用合约方法: get
 myContract.methods.get().call({}, function(error, result){
     console.log(error,result)
 })
 // 调用合约方法: doTransfer
 myContract.methods.doTransfer('0xef6a214542A5371F321a3e457EeC76DA2b4b3C34').send({value: 10**18}, function(error, transactionHash){
     console.log(error,transactionHash)
 })
 // 调用合约方法: getBalance
 myContract.methods.getBalance('0xef6a214542A5371F321a3e457EeC76DA2b4b3C34').call({}, function(error, result){
     console.log(error,result)
 })
 /// --- web3.eth.accounts
 /// 获取私钥对应的账号地址
 var ret = web3.eth.accounts.privateKeyToAccount('a4e22ce0212b565b6e08a67147b3b1b233542912bc0992bb86d240db2deca819');
 console.log(ret.address)
 /// --- web3.utils
 /// 判断地址是否有效
 var ret = web3.utils.isAddress('0xc1912fee45d61c87cc5ea59dae31190fffff232d')
 console.log(ret)
 /// 将 ether 转换为 wei
 var ret = web3.utils.toWei('1', 'ether')
 console.log(ret)
 /// 将 wei 转换为 ether
 var ret = web3.utils.fromWei('1', 'ether')
 console.log(ret)

EIP-712签名/验签：

1. Sign.sol：

    // SPDX-License-Identifier: GPL-3.0
    pragma solidity ^0.8.0;
    import "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
    import "@openzeppelin/contracts/utils/cryptography/draft-EIP712.sol";
    contract Sign is EIP712 {
        constructor(string memory name, string memory version) EIP712(name, version) {
        }
        // 获取签名人（V4）
        function recoverV4(
            address from,
            address to,
            uint256 value,
            bytes memory signature
        ) internal view returns (address) {
            bytes32 digest = _hashTypedDataV4(keccak256(abi.encode(
                    keccak256("Mail(address from,address to,uint256 value)"),
                    from,
                    to,
                    value
                )));
            return ECDSA.recover(digest, signature);
        }
        // 验签
        function verify(
            address from,
            address to,
            uint256 value,
            bytes memory signature
        ) public view returns (bool) {
            address signer = recoverV4(from, to, value, signature);
            return signer == from;
        }
        // 获取 chain id
        function getChainId() public view returns(uint256) {
            return block.chainid;
        }
    }

2. index.js：

    // 创建web3对象
    var Web3 = require('web3');
    var sigUtil = require("eth-sig-util")
    var provider = new Web3.providers.HttpProvider("http://localhost:8545");
    var web3 = new Web3(provider);
    // ---
    var account = "0x3aef6cef1d29bc247b076fe3eeb3018c5684c6d6";
    var accountTo = "0xa3f3749e212bfd54a2fde91038138e9ffea29713";
    var _value = 12345;
    var privateKey = "53395cf932f2e7ca0146a9fac6f2fa0a1fcb92dd13b015e4e98a051a66388ba8";
    var privateKeyHex = Buffer.from(privateKey, 'hex');
    var chainId = 1337;
    // ---
    var contractJson = require("./build/contracts/Sign.json");
    var contractAddr = '0x9cc4EB448e0a6ddcd56783527f6AA370e2C6e4F0';
    var demoContract = new web3.eth.Contract(contractJson.abi, contractAddr);
    // 获取链ID
    demoContract.methods.getChainId().call({from: account}, function(error, result){
        if (error) {
            console.log(error);
        }
        console.log("getChainId:", result);
    });
    // 构造结构体
    const typedData = {
        types: {
            EIP712Domain: [
                { name: 'name', type: 'string' },
                { name: 'version', type: 'string' },
                { name: 'chainId', type: 'uint256' },
                { name: 'verifyingContract', type: 'address' },
            ],
            Mail: [
                { name: 'from', type: 'address' },
                { name: 'to', type: 'address' },
                { name: 'value', type: 'uint256' },
            ],
        },
        domain: {
            name: 'Demo',
            version: '1.0',
            chainId: chainId,
            verifyingContract: contractAddr,
        },
        primaryType: 'Mail',
        message: {
            from: account,
            to: accountTo,
            value: _value,
        },
    }
    // javascript-V4签名
    var signature = sigUtil.signTypedData_v4(privateKeyHex, { data: typedData })
    console.log("signature:", signature)
    // javascript-V4验签
    const recovered = sigUtil.recoverTypedSignature_v4({
        data: typedData,
        sig: signature,
    });
    console.log("recovered：", recovered)
    // solidity-V4验签
    demoContract.methods.verify(typedData.message.from, typedData.message.to, typedData.message.value, signature).call({from: account}, function(error, result){
        if (error) {
            console.log(error);
        }
        console.log("verify：", result);
    });