（中间值）.toBigNumber 不是函数

我包含了这个版本的 web3 而不是 v=1.0.0

https://cdn.jsdelivr.net/gh/ethereum/web3.js@0.20.6/dist/web3.min.js

这解决了问题

根本原因是因为教程使用旧版本的库，

我正在尝试相同的教程，遇到相同的问题并通过以下方式修复

1.更新包版本

     "devDependencies": {
    "bootstrap": "4.1.3",
    "chai": "^4.1.2",
    "chai-as-promised": "^7.1.1",
    "chai-bignumber": "^2.0.2",
    "lite-server": "^2.3.0",
    "nodemon": "^1.17.3",
    "truffle": "^5.4.9",
    "@truffle/contract": "4.3.33",
    "web3": "1.5.2"
  }

2. 更新 index.html

   
   <!-- Include all compiled plugins (below), or include individual files as needed -->
   <script src="vendor/bootstrap/dist/js/bootstrap.min.js"></script>
   <script src="vendor/web3/dist/web3.min.js"></script>
   <script src="vendor/@truffle/contract/dist/truffle-contract.min.js"></script>
   <script src="app.js"></script>

3. 更新 loadWeb3 函数，使用  [this link](https://gist.githubusercontent.com/bitpshr/076b164843f0414077164fe7fe3278d9/raw/74c33baff7d2764d970749b95580cf368f14181a/provider-enable.js)  中的函数

 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!');
 }

``` 

});

4.更新loadContract函数

App.contracts.TodoList.setProvider(new Web3.providers.HttpProvider("http://127.0.0.1:7545"));

5.尝试重启浏览器看看

正如 Mikko 指出的，请使用最新的库（v1.2）

也可以作为 BigNumber 在 web3.utils 中使用“BN”。 web3.utils.toBN(number)

我做了同样的教程，这就是我修复所有错误的方法

app.js

App = {
    contracts: {},
    loading: false,

    load: async () => {
        await App.loadWeb3();
        await App.loadAccounts();
        await App.loadContract();
        await App.render();
    },

      // https://medium.com/metamask/https-medium-com-metamask-breaking-change-injecting-web3-7722797916a8
    loadWeb3: async () => {
         window.addEventListener('load', async () => {
        // Modern dapp browsers...
        if (window.ethereum) {
            window.web3 = new Web3(ethereum);
            console.log("Loaded....")
            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!');
        }
        });
    },

    loadAccounts: async () => {
        // connect to all the accounts, we want index 0 since, its the first account
        // the account we are connected to
        App.account = await ethereum.request({ method: 'eth_accounts' });
        console.log(App.account);
    },

    loadContract: async () => {
        // create a JS version of the contracts
        const todoList = await $.getJSON('TodoList.json')
        App.contracts.TodoList = TruffleContract(todoList)
        App.contracts.TodoList.setProvider(new Web3.providers.HttpProvider("http://127.0.0.1:7545"));
        // console.log(todoList);

        // Hydrate the smart contract with values from the blockchain
        App.todoList = await App.contracts.TodoList.deployed()
    },

    render: async () => {
        if (App.loading) {
            return;
        }

        // Update app loading state
        App.setLoading(true)

        // Render Account
        $('#account').html(App.account)

        // Render Tasks
        await App.renderTasks()

        // Update loading state
        App.setLoading(false)
        },

    renderTasks: async () => {
        // load all the tasks from the blockchain
        const taskCount = await App.todoList.taskCount();
        const $tackTemplate = $(".taskTemplate");

        // render each of the tasks
        for (var i = 1; i <= taskCount; i++){
            const task = await App.todoList.tasks(i);
            const task_id = task[0].toNumber();
            const task_content = task[1];
            const task_completed = task[2];

            // Create the html for the task
            const $newTaskTemplate = $tackTemplate.clone()
            $newTaskTemplate.find('.content').html(task_content)
            $newTaskTemplate.find('input')
                            .prop('name', task_id)
                            .prop('checked', task_completed)
                            .on('click', App.toggleCompleted)

            // Put the task in the correct list
            if (task_completed) {
                $('#completedTaskList').append($newTaskTemplate)
            } else {
                $('#taskList').append($newTaskTemplate)
            }

            // Show the task
            $newTaskTemplate.show()
        }

    },

    setLoading: (boolean) => {
        App.loading = boolean;
        const loader = $('#loader');
        const content = $('#content');
        if (boolean) {
            loader.show();
            content.hide();
        } else {
            loader.hide();
            content.show();
        }
    },

    createTask: async () => {
        App.setLoading(true);
        const content = $('#newTask').val();
        await App.todoList.createTask(content, { from: App.account[0] });
        window.location.reload();
    },

    toggleCompleted: async (e) => {
        App.setLoading(true)
        const taskId = e.target.name
        await App.todoList.toggleCompleted(taskId, { from: App.account[0] });
        window.location.reload()
    },

}

$(() => {
    $(window).load(() => {
        App.load();
    })
})

这是我使用的依赖项列表：

{
  "name": "eth-todo-list",
  "version": "1.0.0",
  "description": "Blockchain Todo List Powered By Ethereum",
  "main": "truffle-config.js",
  "directories": {
    "test": "test"
  },
  "scripts": {
    "dev": "lite-server",
    "test": "echo "Error: no test specified" && sexit 1"
  },
  "author": "gregory@dappuniversity.com",
  "license": "ISC",
  "devDependencies": {
    "bootstrap": "4.1.3",
    "chai": "^4.1.2",
    "chai-as-promised": "^7.1.1",
    "chai-bignumber": "^2.0.2",
    "lite-server": "^2.3.0",
    "nodemon": "^1.17.3",
    "truffle": "^5.4.9",
    "@truffle/contract": "4.3.33",
    "web3": "1.5.2"
  },
  "dependencies": {
    "web3": "^1.7.0"
  }
}