When i am trying to run this code i am getting the

问题:

I am trying to connect mongodb database by this code but when running this code I get the error(error at the bottom of the code). One of the error was in the 7th line where it was resolved by adding { useNewUrlParser: true } but still it has more errors. I am using MongoDB version 4.0.1. Do anybody know how to resolve this error.

const express = require('express');     
const mongoose = require('mongoose');  
const bodyParser = require('body-parser');   
const app = express();

app.use(express.static('public'));  
app.set('view engine','ejs');

mongoose.connect('mongod://localhost/students', { useNewUrlParser: true });  
var studentSchema = new mongoose.Schema({  
    name: String,  
    age:Number,  
    country:String  
});

var Student = mongoose.model("Student", studentSchema);  
var shashank = new Student({  
    name:"Shashank",  
    age:"21",  
    country:"India"  
});    

shashank.save((err,student) => {    
    if(err){     
        console.log('Something went wrong!');     
    }    
    else {      
        console.log("You added: " + student);      
    }      
});      

app.listen(3000,() => {     
    console.log('Server Listening!');     
});

Error while running this code!

D:\HARDWORK\YelpCamp-Course>node app.js
Server Listening!
                                                                                               (node:14060) UnhandledPromiseRejectionWarning: MongoParseError: Invalid connection string
    at parseConnectionString (D:\HARDWORK\YelpCamp-Course\node_modules\mongodb-core\lib\uri_parser.js:216:21)
    at connect (D:\HARDWORK\YelpCamp-Course\node_modules\mongodb\lib\operations\mongo_client_ops.js:179:3)
    at connectOp (D:\HARDWORK\YelpCamp-Course\node_modules\mongodb\lib\operations\mongo_client_ops.js:283:3)
    at executeOperation (D:\HARDWORK\YelpCamp-Course\node_modules\mongodb\lib\utils.js:420:24)
    at MongoClient.connect (D:\HARDWORK\YelpCamp-Course\node_modules\mongodb\lib\mongo_client.js:168:10)
    at Promise (D:\HARDWORK\YelpCamp-Course\node_modules\mongoose\lib\connection.js:499:12)
    at new Promise (<anonymous>)
    at NativeConnection.Connection.openUri (D:\HARDWORK\YelpCamp-Course\node_modules\mongoose\lib\connection.js:496:19)
    at Mongoose.connect (D:\HARDWORK\YelpCamp-Course\node_modules\mongoose\lib\index.js:229:15)
    at Object.<anonymous> (D:\HARDWORK\YelpCamp-Course\app.js:9:10)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
(node:14060) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 3)                                                                                                                (node:14060) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

回答1:

mongoose.connect('mongod://localhost/students', { useNewUrlParser: true }); 

It should start with mongodb://..., And When you use { useNewUrlParser: true } you should always specify the port number in connection string mongoose reference like given below.

mongoose.connect('mongodb://localhost:27017/students', { useNewUrlParser: true });

here port number 27017 is the default port for MongoDB database.