我知道这个问题已经存在，而且之前也有人发过帖子，但我无法让它工作，所以很抱歉问这个问题。

我正在使用 Heroku 来构建和部署，这不是在本地完成的。

我正在尝试让 MetaMask 在我的 Dapp 中得到识别，我正在使用 MetaMask 生成的代码来修复他们的隐私模式重大更改，但我无法克服“web3”、“Web3”和“ethereum”未定义的编译错误。我不明白它需要在我的应用程序中放在哪里。任何帮助都将不胜感激。非常感谢。

这是我的 app.js：

    import React, { Component } from 'react'
    import './App.css'
    import Navbar from './Navbar'
    import Content from './Content'
    import { connect } from 'react-redux'
    import {
      loadWeb3,
      loadAccount,
      loadToken,
      loadExchange
    } from '../store/interactions'
    import { contractsLoadedSelector } from '../store/selectors'


    window.addEventListener('load', async () => {
        // Modern dapp browsers...
        if (window.ethereum) {
            window.web3 = new Web3(ethereum);
            try {
                // Request account access if needed
                await ethereum.enable();
                // Acccounts now exposed
                web3.eth.sendTransaction({/* ... */});
            } catch (error) {
                // User denied account access...
            }
        }
        // Legacy dapp browsers...
        else if (window.web3) {
            window.web3 = new Web3(web3.currentProvider);
            // Acccounts always exposed
            web3.eth.sendTransaction({/* ... */});
        }
        // Non-dapp browsers...
        else {
            console.log('Non-Ethereum browser detected. You should consider trying MetaMask!');
        }
    });

    class App extends Component {
      componentWillMount() {
        this.loadBlockchainData(this.props.dispatch)
      }

      async loadBlockchainData(dispatch) {
        const web3 = loadWeb3(dispatch)
        await web3.eth.net.getNetworkType()
        const networkId = await web3.eth.net.getId()
        await loadAccount(web3, dispatch)
        const token = await loadToken(web3, networkId, dispatch)
        if(!token) {
          window.alert('Token smart contract not detected on the current network. Please select another network with Metamask.')
          return
        }
        const exchange = await loadExchange(web3, networkId, dispatch)
        if(!exchange) {
          window.alert('Exchange smart contract not detected on the current network. Please select another network with Metamask.')
          return
        }

      }

      render() {
        return (
          <div>
            <Navbar />
            { this.props.contractsLoaded ? <Content /> : <div className="content"></div> }
          </div>
        );
      }
    }


    export default connect(mapStateToProps)(App)
    });