我最近遇到了上述问题中提到的终端或命令提示符中弹出的错误。
显示的确切错误是：
const taskCollection = db.collection('tasks');
^
TypeError: Cannot read properties of undefined (reading 'collection')
at Command.<anonymous> (C:\Abc\xyz\Task-Manager-CLI-Project\index.js:50:31)
at Command.listener [as _actionHandler] (C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:494:17)
at C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:1296:65
at Command._chainOrCall (C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:1193:12)
at Command._parseCommand (C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:1296:27)
at C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:1082:27
at Command._chainOrCall (C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:1193:12)
at Command._dispatchSubcommand (C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:1078:25)
at Command._parseCommand (C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:1264:19)
at Command.parse (C:\Abc\xyz\Task-Manager-CLI-Project\node_modules\commander\lib\command.js:910:10)
这是一个简单的任务管理器 CLI 项目。我已将 mongoDB 与我的项目连接，但仍然显示相同的错误，但我不明白错误在哪里？怎么解决呢 这是我的 2 个代码文件：
db.js
const { MongoClient } = require('mongodb');
const uri = 'mongodb://localhost:27017';
//we have used MongoDB Node.js driver to connect js to MongoDB database.
const client = new MongoClient(uri)
let db;
async function connect(){
try{
await client.connect();
db = client.db('task_manager_db');
// it is selecting the database named 'taskmanager'. If the specified database does not exist, MongoDB will create it when you first write data to it.
//now variable db holds the reference to 'taskmanager' database
console.log('Connected to the database');
} catch(err){
console.log('Error connecting to the database...', err);
}
}
function getDB(){
return db;
}
module.exports = {connect, getDB};
index.js
//using commander.js library for the project
//commander.js library provides functions that can run the project on CLI mode.
//Which is the ultimate aim and learning behind the project: To create and run a project using CLI.
const program = require('commander');
//importing the functions from db.js
const {connect, getDB} = require('./db');
program
.version('1.0.0')
.description('Task Manager CLI')
//connecting MongoDB database (i.e. to the uri to be specific)
.action(connect());
//general structure of defining commands for CLI using commander.js library
// program
// .command('')
// .description('')
// .action(//function inside() => { });
//command to list all tasks --> list
program
.command('list')
.description('list of commands')
.action(async() => {
//extract database from function
const db = getDB();
//refer to the collection in db
const taskCollection = db.collection('tasks');
try{
const tasks = await taskCollection.find().toArray();
console.log("Listing all the tasks:");
tasks.forEach((task_) => {
console.log(`- ${tasks.task_}`);
});
}catch(err){
console.log("Error displaying tasks...");
}
});
//command to add a task --> add <taskname>
program
.command('add <taskname>')
.description('Add a new task')
.action(async() => {
const db = getDB();
const taskCollection = db.collection('tasks');
try{
const result = await taskCollection.insertOne({ taskname });
console.log(`New Task added: ${task} TaskID: ${result.insertedId}`);
}catch(err){
console.log("Error adding task...", err);
}
});
//command to delete task --> delete <TaskId>
program
.command("delete <TaskId>")
.description("Delete a task")
.action(async() => {
const db = getDB();
const taskCollection = await db.collection('tasks');
try{
const result = await tasksCollection.deleteOne({ _id: new ObjectId(TaskId) });
console.log(`Deleted Task (ID: ${TaskId}`);
}catch(err){
console.log("Error deleting a task...", err);
}
});
program.parse(process.argv);
我尝试从 MongoDB 指南针更改 URI，甚至将其从 “New Connection” 重命名为 “Project1”，然后将 URI 复制到 db.js 文件。没成功。
我尝试将 URI 从 mongodb://localhost:27017 更改为 mongodb://localhost:27018 OR从mongodb://localhost:27017到mongodb://localhost:27017/Project1仍然不起作用。错误仍然出现。
预期输出是命令 list、add 、delete 应在命令提示符下运行并显示编码的 console.log() 输出或错误处理输出。相反，它说我的数据库task_manager_db的集合tasks未定义，因此无法读取其属性。
由于
connect()dbawaitindex.jsdb.js
const { MongoClient } = require('mongodb');
const uri = 'mongodb://localhost:27017';
const client = new MongoClient(uri)
let db;
async function connect(){
try{
await client.connect();
db = client.db('task_manager_db');
return db;
} catch(err){
console.log('Error connecting to the database...', err);
}
}
module.exports = {connect};
index.js
const program = require('commander');
const {connect} = require('./db');
program
.version('1.0.0')
.description('Task Manager CLI');
program
.command('list')
.description('list of commands')
.action(async() => {
const db = await connect();
const taskCollection = db.collection('tasks');
try{
const tasks = await taskCollection.find().toArray();
console.log("Listing all the tasks:");
tasks.forEach((task_) => {
console.log(`- ${tasks.task_}`);
});
}catch(err){
console.log("Error displaying tasks...");
}
});
program
.command('add <taskname>')
.description('Add a new task')
.action(async() => {
const db = await connect();
const taskCollection = db.collection('tasks');
try{
const result = await taskCollection.insertOne({ taskname });
console.log(`New Task added: ${task} TaskID: ${result.insertedId}`);
}catch(err){
console.log("Error adding task...", err);
}
});
program
.command("delete <TaskId>")
.description("Delete a task")
.action(async() => {
const db = await connect();
const taskCollection = await db.collection('tasks');
try{
const result = await tasksCollection.deleteOne({ _id: new ObjectId(TaskId) });
console.log(`Deleted Task (ID: ${TaskId}`);
}catch(err){
console.log("Error deleting a task...", err);
}
});
program.parse(process.argv);