[区块链笔记11] web3.js实用代码段

检查环境web3环境

window.addEventListener('load', function() { if (typeof web3 !== 'undefined') { web3 = new Web3(web3.currentProvider); if (web3.currentProvider.isMetaMask == true) { //metamask可用 } else { //非metamask环境 } } else { //需要安装metamask } })

检查网络环境

web3.version.getNetwork((err, netId) => { switch (netId) { case '1': //mainnet break case '2': //deprecated morden test network break case '3': //ropsten test network break case '4': //Rinkeby test network break default: console.log('This is an unknown network.'); } });

获取账户信息

//0.20.x版本 '<script src="https://cdn.jsdelivr.net/gh/ethereum/web3.js@0.20.6/dist/web3.min.js"></script>' ethereum.enable(); if (typeof web3 !== 'undefined') { web3 = new Web3(web3.currentProvider); } else { web3 = new Web3(new Web3.providers.HttpProvider('http:127.0.0.1:7545')); console.log('web3 local provider:' + web3); } var accounts = web3.eth.accounts; console.log('accounts[0]: ' + accounts); web3.eth.getAccounts(function callback1(err1, result) { web3.eth.getBalance(result[0], function callback2(err2, value) { $('#info').html(value); }) }) //1.x.x版本 '<script src="https://cdn.jsdelivr.net/gh/ethereum/web3.js@1.0.0-beta.36/dist/web3.min.js"></script>' ethereum.enable(); if (typeof web3 !== 'undefined') { web3 = new Web3(web3.currentProvider); } else { web3 = new Web3(new Web3.providers.HttpProvider('http:127.0.0.1:7545')); console.log('web3 local provider:' + web3); } web3.eth.getAccounts() .then((res) => web3.eth.getBalance(res[0])) .then((value) => $('#info').html(value));

部署合约

var infoContract = web3.eth.contract(ABI); var info = infoContract.at("address")； //这部分代码可以通过remix获取 infoContract.new({ from: mySenderAddress, data:bytecode, gas:gasEstimate });

调用合约

info.getInfo(function(err, result) { }) info.setInfo(name, age, function(err, result) { })

发送交易

//检查钱包 web3.eth.getAccounts(function(err, accounts) { //检查accounts内容 }) //自动指定gas var message = {from: fromAccount, to:toAccount, value:web3.toWei(amount, 'ether'), gas:gas, gasPrice:gasPrice}; //使用默认账号 web3.eth.defaultAccount = fromAccount; var message = {to:toAccount, value:web3.toWei(amount, 'ether')}; web3.eth.sendTransaction(message, (err, res) => { var output = ""; if (!err) { output += res; } else { output = "Error"; } document.getElementById('transactionResponse').innerHTML = "Transaction response " + output + "<br/>" });

监听事件

合约中设置事件 event EventName(uint param); 合约中触发事件 emit EventName(10);

pragma solidity ^0.4.23; contract InfoContract { string name; uint age; event doneEvent(string name, uint age); function setInfo(string _name, uint _age) public { name = _name; age = _age; emit doneEvent(name, age); } function getInfo() public view returns (string, uint) { return (name, age); } } var infoEvent = info.doneEvent(); infoEvent.watch(function(error, result) { if (!error) { //$('#loader').hide(); $('#info').html(result.args.name + '(' + result.args.age + ' years old)'); } else { //$('#loader').hide(); $('#info').hmtl('Error:' + error); } })

最后这个监听事件的地方出了一点问题，就是var infoEvent = info.doneEvent();这行代码中，js的console里说donEvent不是一个函数。搞了半天都没搞好 后来从谷歌换成了火狐就好了。