JAVASCRIPT

MongoServerSelectionError: connect ECONNREFUSED ::1:27017

// instead of this
const url = "mongodb://localhost:27017";

// Just Replace
const url = "mongodb://0.0.0.0:27017";

MongooseServerSelectionError: connect ECONNREFUSED ::1:27017

// Try using 127.0.0.1 instead of localhost in connection url
// mongodb://localhost:27017
// mongodb://127.0.0.1:27017

const mongoose = require('mongoose');

mongoose.connect('mongodb://127.0.0.1:27017').then(() => {
    console.log("connected to database");
})

(node:15855) UnhandledPromiseRejectionWarning: MongooseServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017

mongodb://localhost:27017/{DATABASE_NAME}

MongooseServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017

This happened probably because the MongoDB service isn't started. Follow the below steps to start it:

Go to Control Panel and click on Administrative Tools.
Double click on Services. A new window opens up.
Search MongoDB.exe. Right click on it and select Start.
The server will start. Now execute npm start again and the code might work this time.

MongoNetworkError: connect ECONNREFUSED 127.0.0.1:27017

Check if you've installed mongoDB by running "mongod" in your terminal