[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。