Next simply allows the next route handler in line to handle the request. In this case, if the user id exists, it will likely use res. send to complete the request. If it doesn’t exist, there is likely another handler that will issue an error and complete the request then.

What is middleware in NodeJS?

Middleware functions are functions that have access to the request object ( req ), the response object ( res ), and the next middleware function in the application’s request-response cycle. The next middleware function is commonly denoted by a variable named next .

What is Mongoose in node JS?

Mongoose is an Object Data Modeling (ODM) library for MongoDB and Node. js. It manages relationships between data, provides schema validation, and is used to translate between objects in code and the representation of those objects in MongoDB.

What is next function Express?

The next function is a function in the Express router which, when invoked, executes the middleware succeeding the current middleware. Middleware functions can perform the following tasks: Execute any code. Make changes to the request and the response objects.

What is JWT in node JS?

JSON Web Token is an open standard for securely transferring data within parties using a JSON object. JWT is used for stateless authentication mechanisms for users and providers, this means maintaining session is on the client-side instead of storing sessions on the server.

What is middleware function?

Middleware functions are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle. These functions are used to modify req and res objects for tasks like parsing request bodies, adding response headers, etc.

What is Express router () in node JS?

Express is one of the popular web framework for Node. js. … Express router is a class which helps us to create router handlers. By router handler i mean to not just providing routing to our app but also can extend this routing to handle validation, handle 404 or other errors etc.

Is MongoDB a framework?

MongoDB is a source-available cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with optional schemas. MongoDB is developed by MongoDB Inc. and licensed under the Server Side Public License (SSPL).

What is promise in node JS?

A Promise in Node means an action which will either be completed or rejected. In case of completion, the promise is kept and otherwise, the promise is broken. So as the word suggests either the promise is kept or it is broken. And unlike callbacks, promises can be chained.

Which is better MongoDB or mongoose?

It provides a lot of convenience in the creation and management of data in MongoDB. On the downside, learning mongoose can take some time, and has some limitations in handling schemas that are quite complex. However, if your collection schema is unpredictable, or you want a Mongo-shell like experience inside Node.

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Can I use MongoDB without mongoose?

Yes, of course, drivers provide many advantages to make our lives easy. But to keep things simple and lightweight we can use only MongoDB for CRUD operation without a mongoose. What about validation? Don’t worry, packages like sanitize-html can be used in MongoDB to validate data before storing to a database.

Why is JWT used?

Information Exchange: JWTs are a good way of securely transmitting information between parties because they can be signed, which means you can be sure that the senders are who they say they are. Additionally, the structure of a JWT allows you to verify that the content hasn’t been tampered with.

What is Bcrypt in node JS?

Bcrypt is a popular and trusted method for salt and hashing passwords. You have learned how to use bcrypt’s NodeJS library to salt and hash a password before storing it in a database. You have also learned how to use the bcrypt compare function to compare a password to a hash, which is necessary for authentication.

How does JWT work in NodeJS?

JWT specifies a compact and self-contained method for communicating information as a JSON object between two parties. Because it is signed, this information can be checked and trusted. JWTs can be signed using a secret (using the HMAC algorithm) or an RSA or ECDSA public/private key combination.

What does res render do?

The res. render() function is used to render a view and sends the rendered HTML string to the client.

What is the difference between Express () and Express router ()?

The main difference is that express() is a top level function, which means it performs core functionality for the library and it contains its own methods where, as a matter of fact, Router is one, and that is why when we create a specific router we chain the Router() method on express , kind of like how we use app.

What does res JSON () do?

json() Function. The res. json() function sends a JSON response. This method sends a response (with the correct content-type) that is the parameter converted to a JSON string using the JSON.

Why we use Express in node JS?

Express. js basically helps you manage everything, from routes, to handling requests and views. Redis is a key/value store — commonly used for sessions and caching in Node. js applications.

What is req and res in node JS?

The req object represents the HTTP request and has properties for the request query string, parameters, body, and HTTP headers. The res object represents the HTTP response that an Express app sends when it gets an HTTP request.

What is event loop in Nodejs?

Event loop is an endless loop, which waits for tasks, executes them and then sleeps until it receives more tasks. The event loop executes tasks from the event queue only when the call stack is empty i.e. there is no ongoing task. The event loop allows us to use callbacks and promises.

What is callback and promise?

The Promise object is created using the new keyword and contains the promise ; this is an executor function which has a resolve and a reject callback. As the names imply, each of these callbacks returns a value with the reject callback returning an error object.

What is callback function in JavaScript?

In JavaScript, a callback is a function passed into another function as an argument to be executed later. … When you pass a callback function into another function, you just pass the reference of the function i.e., the function name without the parentheses () .

What is callback function and how it works?

A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action. … A good example is the callback functions executed inside a . then() block chained onto the end of a promise after that promise fulfills or rejects.

When should I use Cassandra?

It makes sense to use Cassandra when you have a huge amount of data, a huge number of queries but very little variety of queries. Cassandra basically works by partitioning and replicating. If all your queries will be based on the same partition key, Cassandra is your best bet.

What does Mern stack?

MERN stands for MongoDB, Express, React, Node, after the four key technologies that make up the stack. MongoDB – document database. Express(.js) – Node.js web framework. React(.js) – a client-side JavaScript framework. Node(.js) – the premier JavaScript web server.

Is MongoDB a NoSQL?

NoSQL databases come in a variety of types including document databases, key-values databases, wide-column stores, and graph databases. MongoDB is the world’s most popular NoSQL database.

What is NoSQL vs SQL?

SQL pronounced as “S-Q-L” or as “See-Quel” is primarily called RDBMS or Relational Databases whereas NoSQL is a Non-relational or Distributed Database. Comparing SQL vs NoSQL database, SQL databases are table based databases whereas NoSQL databases can be document based, key-value pairs, graph databases.

What is MongoDB compass?

MongoDB Compass is a powerful GUI for querying, aggregating, and analyzing your MongoDB data in a visual environment. Compass is free to use and source available, and can be run on macOS, Windows, and Linux.

What is MongoDB vs MySQL?

MongoDB is an open-source database developed by MongoDB, Inc. MongoDB stores data in JSON-like documents that can vary in structure. … MySQL is a popular open-source relational database management system (RDBMS) that is developed, distributed and supported by Oracle Corporation.

What is Mongoose NPM?

Mongoose is a Object Data Modeling (ODM) library for MongoDB distributed as an npm package. … js driver together with MongoDB Schema Validation. We’ll see how the MongoDB Schema Validation helps us enforce a database schema, while still allowing for great flexibility when needed.

What is Mongoose Express?

Mongoose: Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Waterline: An ORM extracted from the Express-based Sails web framework.