在进行网站或客户端开发时，就需要用到web3.js。web3.js库是一个javascript库，可以让你执行很多与区块链进行交互的任务。与Ajax类似，可以使用Web3.js读写以太坊区块链。
区块链网络是一个点对点的对等网络，网络由各个节点相互连接构成，智能合约的代码与数据存储在区块链中。使用web3.js可以向区块链网络中某个以太坊节点发出请求，与区块链网络进行交互。
web3.js使用JSON RPC与Ethereum区块链通信(JSON RPC即JSON远程调用)，对区块链网络进行数据读写。这有点像使用jQuery ajax库来读写web服务器上的数据。
这里记录一下Web3.js的常用操作。
一、通过npm安装
npm install --save web3@0.20
有了这个Web3以太坊编程接口，就可以与以太坊主网进行通信。
二、访问节点
const Web3 = require(‘web3‘) const rpcURL = ‘‘ // RPC URL const web3 = new Web3(rpcURL) const address = ‘‘ // 账户地址 // 读取address中的余额，余额单位是wei web3.eth.getBalance(address, (err, wei) => { // 余额单位从wei转换为ether balance = web3.utils.fromWei(wei, ‘ether‘) console.log("balance: " + balance) })
三、调用读取智能合约
const Web3 = require(‘web3‘) const rpcURL = ‘‘ // Your RCP URL goes here const web3 = new Web3(rpcURL) const abi = [{"constant":true,"inputs":[],"name":"mintingFinished","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"name","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_spender","type":"address"},{"name":"_value","type":"uint256"}],"name":"approve","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"totalSupply","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_from","type":"address"},{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"name":"transferFrom","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"unpause","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_amount","type":"uint256"}],"name":"mint","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"paused","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"_owner","type":"address"}],"name":"balanceOf","outputs":[{"name":"balance","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"finishMinting","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":false,"inputs":[],"name":"pause","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"owner","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"symbol","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_value","type":"uint256"}],"name":"transfer","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_amount","type":"uint256"},{"name":"_releaseTime","type":"uint256"}],"name":"mintTimelocked","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"_owner","type":"address"},{"name":"_spender","type":"address"}],"name":"allowance","outputs":[{"name":"remaining","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"newOwner","type":"address"}],"name":"transferOwnership","outputs":[],"payable":false,"type":"function"},{"anonymous":false,"inputs":[{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Mint","type":"event"},{"anonymous":false,"inputs":[],"name":"MintFinished","type":"event"},{"anonymous":false,"inputs":[],"name":"Pause","type":"event"},{"anonymous":false,"inputs":[],"name":"Unpause","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"owner","type":"address"},{"indexed":true,"name":"spender","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Approval","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"from","type":"address"},{"indexed":true,"name":"to","type":"address"},{"indexed":false,"name":"value","type":"uint256"}],"name":"Transfer","type":"event"}] const address = ‘0xd26114cd6EE289AccF82350c8d8487fedB8A0C07‘ const contract = new web3.eth.Contract(abi, address) contract.methods.totalSupply().call((err, result) => { console.log(result) }) contract.methods.name().call((err, result) => { console.log(result) }) contract.methods.symbol().call((err, result) => { console.log(result) }) contract.methods.balanceOf(‘0xd26114cd6EE289AccF82350c8d8487fedB8A0C07‘).call((err, result) => { console.log(result) })
四、准备账号
> node > web3.eth.accounts.create() Thrown: ReferenceError: web3 is not defined > const Web3 = require(‘web3‘) undefined > const web3 = new Web3(‘https://ropsten.infura.io/v3/YOUR_INFURA_API_KEY‘) undefined > web3.eth.accounts.create() { address: ‘0xf4Ab5314ee8d7AA0eB00b366c52cEEccC62d6B4B‘, privateKey: ‘0xb75e2bcaec74857cf9bb6636d66a04784d4c0fcfd908f4a2bc213428eba5af0d‘, signTransaction: [Function: signTransaction], sign: [Function: sign], encrypt: [Function: encrypt] } > web3.eth.accounts.create() { address: ‘0xff96B8B43ECd6C49805747F94747bFfa3A960b69‘, privateKey: ‘0xac0adfdbaeb0770a479e79aac78779d82fdc2f9262e0c8f751ae70fb63ef6196‘, signTransaction: [Function: signTransaction], sign: [Function: sign], encrypt: [Function: encrypt] } >
五、执行交易
var Tx = require(‘ethereumjs-tx‘).Transaction
const Web3 = require(‘web3‘)
const web3 = new Web3(‘https://ropsten.infura.io/v3/YOUR_INFURA_API_KEY‘)
const account1 = ‘0xf4Ab5314ee8d7AA0eB00b366c52cEEccC62d6B4B‘ // Your account address 1
const account2 = ‘0xff96B8B43ECd6C49805747F94747bFfa3A960b69‘ // Your account address 2
const pk1 = ‘b75e2bcaec74857cf9bb6636d66a04784d4c0fcfd908f4a2bc213428eba5af0d‘ // 实际项目中应该从process.env.PRIVATE_KEY_1中读取
const pk2 = ‘ac0adfdbaeb0770a479e79aac78779d82fdc2f9262e0c8f751ae70fb63ef6196‘ // 实际项目中应该从process.env.PRIVATE_KEY_2中读取
const privateKey1 = Buffer.from(pk1, ‘hex‘)
const privateKey2 = Buffer.from(pk2, ‘hex‘)
web3.eth.getTransactionCount(account1, (err, txCount) => {
// 创建交易对象
const txObject = {
nonce: web3.utils.toHex(txCount),
to: account2,
value: web3.utils.toHex(web3.utils.toWei(‘0.1‘, ‘ether‘)),
gasLimit: web3.utils.toHex(21000),
gasPrice: web3.utils.toHex(web3.utils.toWei(‘10‘, ‘gwei‘))
}
// 签署交易
const tx = new Tx(txObject, { chain: ‘ropsten‘, hardfork: ‘petersburg‘ })
tx.sign(privateKey1)
const serializedTx = tx.serialize()
const raw = ‘0x‘ + serializedTx.toString(‘hex‘)
// 广播交易
web3.eth.sendSignedTransaction(raw, (err, txHash) => {
console.log(‘txHash:‘, txHash)
// 可以去ropsten.etherscan.io查看交易详情
})
})
六、执行部署
var Tx = require(‘ethereumjs-tx‘).Transaction const Web3 = require(‘web3‘) const web3 = new Web3(‘https://ropsten.infura.io/v3/YOUR_INFURA_API_KEY‘) const account1 = ‘0xf4Ab5314ee8d7AA0eB00b366c52cEEccC62d6B4B‘ // Your account address 1 const account2 = ‘0xff96B8B43ECd6C49805747F94747bFfa3A960b69‘ // Your account address 2 const pk1 = ‘b75e2bcaec74857cf9bb6636d66a04784d4c0fcfd908f4a2bc213428eba5af0d‘ // 实际项目中应该从process.env.PRIVATE_KEY_1中读取 const pk2 = ‘ac0adfdbaeb0770a479e79aac78779d82fdc2f9262e0c8f751ae70fb63ef6196‘ // 实际项目中应该从process.env.PRIVATE_KEY_2中读取 const privateKey1 = Buffer.from(pk1, ‘hex‘) const privateKey2 = Buffer.from(pk2, ‘hex‘) web3.eth.getTransactionCount(account1, (err, txCount) => { const data = "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" // 创建交易对象 const txObject = { nonce: web3.utils.toHex(txCount), gasLimit: web3.utils.toHex(1000000), gasPrice: web3.utils.toHex(web3.utils.toWei(‘10‘, ‘gwei‘)), data: data } // 签署交易 const tx = new Tx(txObject, { chain: ‘ropsten‘, hardfork: ‘petersburg‘ }) tx.sign(privateKey1) const serializedTx = tx.serialize() const raw = ‘0x‘ + serializedTx.toString(‘hex‘) // 广播交易 web3.eth.sendSignedTransaction(raw, (err, txHash) => { console.log(‘txHash:‘, txHash) // 可以去ropsten.etherscan.io查看交易详情 }) })
七、执行写函数调用
var Tx = require(‘ethereumjs-tx‘).Transaction const Web3 = require(‘web3‘) const web3 = new Web3(‘https://ropsten.infura.io/v3/YOUR_INFURA_API_KEY‘) const account1 = ‘0xf4Ab5314ee8d7AA0eB00b366c52cEEccC62d6B4B‘ // Your account address 1 const account2 = ‘0xff96B8B43ECd6C49805747F94747bFfa3A960b69‘ // Your account address 2 const pk1 = ‘b75e2bcaec74857cf9bb6636d66a04784d4c0fcfd908f4a2bc213428eba5af0d‘ // 实际项目中应该从process.env.PRIVATE_KEY_1中读取 const pk2 = ‘ac0adfdbaeb0770a479e79aac78779d82fdc2f9262e0c8f751ae70fb63ef6196‘ // 实际项目中应该从process.env.PRIVATE_KEY_2中读取 const privateKey1 = Buffer.from(pk1, ‘hex‘) const privateKey2 = Buffer.from(pk2, ‘hex‘) // 读取已部署的契约 -- 从Etherscan获取地址 const contractAddress = ‘0x30951343d6d80d2c94897f1a81c53cc030aef879‘ const contractABI = [ { "constant": false, "inputs": [ { "internalType": "string", "name": "_value", "type": "string" } ], "name": "set", "outputs": [], "payable": false, "stateMutability": "nonpayable", "type": "function" }, { "constant": true, "inputs": [], "name": "get", "outputs": [ { "internalType": "string", "name": "", "type": "string" } ], "payable": false, "stateMutability": "view", "type": "function" }, { "inputs": [], "payable": false, "stateMutability": "nonpayable", "type": "constructor" } ] const contract = new web3.eth.Contract(contractABI, contractAddress) web3.eth.getTransactionCount(account1, (err, txCount) => { // 创建交易对象 const txObject = { nonce: web3.utils.toHex(txCount), gasLimit: web3.utils.toHex(8000000), gasPrice: web3.utils.toHex(web3.utils.toWei(‘10‘, ‘gwei‘)), to: contractAddress, data: contract.methods.set("qikegu").encodeABI() } // 签署交易 const tx = new Tx(txObject, { chain: ‘ropsten‘, hardfork: ‘petersburg‘ }) tx.sign(privateKey1) const serializedTx = tx.serialize() const raw = ‘0x‘ + serializedTx.toString(‘hex‘) // 广播交易 web3.eth.sendSignedTransaction(raw, (err, txHash) => { console.log(‘txHash:‘, txHash) // 可以去ropsten.etherscan.io查看交易详情 }) })
八、获取事件
// 获取事件 contract.getPastEvents( ‘AllEvents‘, { fromBlock: 8717848, toBlock: ‘latest‘ }, ).then(function(events) { console.log(events) });
九、区块查询
web3.eth.getBlockNumber().then(console.log) // 查询最新区块 web3.eth.getBlock(‘latest‘).then(console.log) // 查询某个区块中的指定交易信息 const hash = ‘0x66b3fd79a49dafe44507763e9b6739aa0810de2c15590ac22b5e2f0a3f502073‘ web3.eth.getTransactionFromBlock(hash, 2).then(console.log)
十、常用工具操作
// 根据最近几个区块，计算平均Gas价格 web3.eth.getGasPrice().then((result) => { console.log("wei: " + result) console.log("ether: " + web3.utils.fromWei(result, ‘ether‘)) }) //评估Gas费 web3.eth.estimateGas({ to: "0x11f4d0A3c12e86B4b5F39B213F7E19D048276DAe", data: "0xc6888fa10000000000000000000000000000000000000000000000000000000000000003" }) .then(console.log);
这个文档可以的，web3.js – 智能合约对象 | 奇客谷教程 ?? (qikegu.com)