简单整合react的合约（二）

创建webClient.js, 将（一）中 export 的代码复制到这个文件

import Web3 from 'web3';
let selectedAccount;

export const init = () => {
    let provider = window.ethereum;

    if(typeof provider !== 'undefined'){
      provider
      .request({method: 'eth_requestAccounts'})
      .then(accounts =>{
        selectedAccount =  accounts[0];
        console.log(`Selected Account is ${selectedAccount}$`);
      }).catch((err)=>{
        console.log(err);
      }); 
      // 监听metamask 账号改变
      window.ethereum.on('accountsChanged', function(accounts){
          selectedAccount = accounts[0];
         console.log(`Selected Account is ${selectedAccount}$`);
      });
    }
    const web3 = new Web3(provider);
};

App.js 修改为

import logo from './logo.svg';
import './App.css';
//import './polyfill.js';
import Web3 from 'web3';
import React, {useEffect} from 'react';
import {init} from './Web3Client'
function App() {

  //const providerUrl = process.env.PROVIDER_URL || 'http://localhost:7545';
  useEffect(() => {
      init();  
  }, []);

  return <div className='App'></div>
}

export default App;

再运行，换个 账号可以看到console 输出账号