MEAN Stack Interview Questions and Answers- Part 4

Answer:

There are many popular DevOps Tools, such as:

• Jenkins
• Docker
• Git
• Selenium
• Nagios
• Puppet, Chef, Ansible

Answer:

A module is a fundamental building block that helps organize and encapsulate components, services, directives, pipes, and other Angular features into cohesive units. It acts as a container for different parts of an Angular application, defining the context in which these components and features operate. Modules are an essential concept in Angular’s architecture and help maintain modularity, reusability, and manage the overall structure of the application.

Answer:

The primary role of a module in Angular is to:

1. Enable reusability: Modules can be imported into other modules, allowing components and services to be reused across multiple parts of the application or even in different projects.
2. Encapsulate functionality: Modules group related components, services, and other features together, providing a clear boundary and separating concerns.
3. Define dependencies: When a module is imported, its dependencies become available within that module, ensuring proper communication and interaction between different parts of the application.
4. Configure the application: Modules can include configuration settings, route definitions, and other application-wide setup code.
5. Provide dependency injection context: Angular’s dependency injection system is based on hierarchical injectors provided by modules. Modules define the context in which services and other providers are available, making it easy to manage and share instances of services within the application.

Answer:

Sharding refers to the process of distributing and partitioning data across multiple machines or servers in a cluster. This approach is used to address scalability and performance challenges that arise when dealing with large volumes of data in a database.

Answer:

The key components of MongoDB’s Sharding architecture are as follows:

1. Shard: A shard is a separate database instance that holds a subset of the data. Each shard is a replica set consisting of multiple servers, which helps in ensuring high availability and fault tolerance.
2. Shard Key: MongoDB uses the shard key to determine which shard should store the data for a given document. Choosing an appropriate shard key is crucial for evenly distributing the data and preventing hotspots.
3. Config Servers: MongoDB uses config servers to store the metadata about the sharded data. This metadata includes information about which data is stored on which shard.
4. Mongos: The mongos process acts as a router in the sharded cluster. It receives client requests and routes them to the appropriate shards based on the shard key. Applications interact with the mongos process instead of directly connecting to individual shards, providing a unified view of the sharded data.

Answer:

To create a new collection in MongoDB, you need to follow these steps:

• Before creating a collection, ensure you have MongoDB installed and running, and you have a connection to the MongoDB server. You can use a MongoDB client like the MongoDB shell, MongoDB Compass, or a driver for your preferred programming language.
• Decide which database you want to create the collection in. If the database does not exist, MongoDB will create it automatically when you create the collection.
• There are multiple ways to create a collection:
• MongoDB Shell
• MongoDB Driver

Answer:

The main purpose of indexing in MongoDB are as follows:

• Faster Queries: Indexes help speed up query execution by providing a way for MongoDB to find and access data more efficiently.
• Improved Performance: By using indexes, read operations, and aggregate can be optimized, leading to reduced response times and improved overall database performance.
• Sorting: Indexes also facilitate efficient sorting of data. If a query requires sorting based on certain fields, an appropriate index can significantly speed up the sorting process.
• Avoiding Full Collection Scans: With indexes in place, MongoDB can avoid performing full collection scans for most queries, making it much more scalable and suitable for handling large amounts of data.
• Unique Constraints: Indexes can enforce uniqueness constraints on fields, ensuring that no two documents in the collection can have the same value for the indexed fields.

Answer:

To backup and restore a MongoDB database, you can use the mongodump and mongorestore utilities that come with MongoDB. These tools allow you to create backups of your databases and restore them when needed.

Answer:

body-parser is a middleware for Node.js web applications, designed to handle HTTP POST requests and parse the request body to make it accessible in a more convenient way. It simplifies the process of working with incoming data from forms, JSON, and other sources in the request body.

Answer:

Creating a simple HTTP server using Node.js is straightforward and can be accomplished with just a few lines of code. Here’s a step-by-step guide on how to do it:

• Install Node.js
• Set up the project directory
• Initialize a new Node.js project
• Install the required dependencies
• Create your HTTP server file
• Write the code for the HTTP server
• Save the file and close the text editor
• Run the server
• Access the server in your browser

Answer:

Here’s a general outline of how you can implement authentication and security measures in each component of the MEAN stack:

1. Enable authentication in MongoDB by setting up username and password-based access to the database. This ensures that only authorized users can connect to the database. Avoid storing sensitive information in plain text. Instead, use hashing algorithms to securely store passwords.
2. Use secure communication by enabling HTTPS to encrypt data transmission between the client and server. Implement middleware for handling CORS to control which domains can access your server’s resources.
3. Use Angular’s built-in HTTP client to send requests securely to the server over HTTPS. Implement CSRF protection by including CSRF tokens. Sanitize user inputs on the client-side to prevent XSS attacks.
4. Secure your Node.js application by using the latest LTS version of Node.js to ensure you receive security updates. Utilize modules like helmetto add security headers to HTTP responses and protect against common vulnerabilities.
5. Consider using JWT for token-based authentication. When a user logs in, generate a JWT that contains the user’s information and an expiration time.

Answer:

The concept of Single Page Applications (SPAs) is a web development approach that aims to provide a smooth and seamless user experience by dynamically updating the content on a single web page, instead of reloading entire new pages when navigating through different sections or performing actions.

Answer:

MEAN Stack is particularly well-suited for building SPAs because it combines a powerful front-end framework (Angular) with a flexible and scalable back-end (Node.js and Express.js). MongoDB, as a NoSQL database, fits well with the JSON data structure used in SPAs, making data manipulation and retrieval more straightforward. When using MEAN Stack to build SPAs, Angular handles the front-end logic, user interface, and interactivity, while Node.js and Express.js take care of serving API endpoints and handling server-side operations. The SPA communicates with the backend through these APIs to request and update data asynchronously, without requiring a full-page refresh.

Answer:

Angular uses a concept called “Two-Way Data Binding” to automatically synchronize data between the model and the view. When the model changes, the view is updated, and when the view changes, the model is updated.

Answer:

The MEAN stack is a combination of popular open-source technologies used to build web applications. It consists of:

• MongoDB: A NoSQL database that stores data in JSON-like documents.
• Express.js: A minimalist web application framework for Node.js, simplifying the server-side logic.
• AngularJS (or Angular): A front-end framework for building dynamic web applications.
• Node.js: A JavaScript runtime that allows server-side execution of JavaScript code.

Answer:

AngularJS and Angular are both front-end frameworks, but they have some significant differences:

• AngularJS is an older version of Angular, while Angular is a complete rewrite and introduces major architectural changes.
• Angular uses TypeScript as its primary language, while AngularJS uses JavaScript.
• AngularJS relies heavily on two-way data binding, whereas Angular favors one-way data binding for better performance.
• Angular is more modular, promoting the use of components, while AngularJS relies on controllers and scope.

Answer:

Authorization is typically done on the server-side, where the server checks the validity of the JWT and the user’s permissions to access specific resources or perform certain actions.

Answer:

Observables are a part of the RxJS library and represent a stream of data over time. They can emit multiple values asynchronously and are cancellable. Observables are widely used in Angular to handle asynchronous operations, like making HTTP requests.

Answer:

To prevent CSRF attacks in Express.js, you can use middleware like “csurf” (CSRF protection middleware). This middleware adds a CSRF token to forms or headers, and the token is then validated on every request to ensure it matches the expected value.

Answer:

MongoDB is a NoSQL database, which means it does not use the traditional tabular structure like SQL databases. Instead, it stores data in JSON-like documents with dynamic schemas, allowing more flexible and scalable data models.