Node.js is a popular, open-source runtime environment for building server-side applications. It is built on Chrome’s V8 JavaScript engine and uses an event-driven, non-blocking I/O model.
During a Node.js interview, you may be asked about your experience with asynchronous programming, the event loop, and the use of modules. You may also be asked about popular libraries and frameworks such as Express, React, and Webpack, as well as your experience working with databases and integrating with third-party APIs.
Here are the frequently asked questions in nodejs interviews. Please note that it is also important to have a strong understanding of JavaScript and you should be able to demonstrate your ability to write efficient, well-structured code.
1. What are some key features of Node.js?
Some key features of Node.js include:
– Asynchronous, non-blocking I/O model
– Single threaded, event-driven architecture
– Built-in support for HTTP, TCP, and DNS protocols
– Supports real-time web applications
– Large and active open-source community
2. How is Node.js different from traditional web servers?
Node.js differs from traditional web servers in a few key ways:
– It uses JavaScript, rather than a language like PHP or Python, as the server-side language.
– It uses a non-blocking, event-driven architecture, which makes it more efficient for handling real-time data.
– It is single threaded, meaning that it can only process one request at a time. This can be both a strength and a weakness, depending on the application.
3. What are some common use cases for Node.js?
Node.js is commonly used for building real-time, data-intensive applications, such as chat applications, online gaming, and streaming platforms. It is also frequently used for building APIs and microservices, as well as for server-side rendering of web applications.
4. How do you handle errors in Node.js?
Errors in Node.js can be handled using the try-catch block or by using the built-in error-handling functions, such as process.on(‘uncaughtException’) or domain.on(‘error’). It is also recommended to use a logging library, such as Winston, to log errors for easier debugging and tracking.
5. How does Node.js handle concurrency?
Node.js uses an event loop and non-blocking I/O to handle concurrency. This means that instead of creating a new thread for each incoming request, the event loop handles the request and moves on to the next one.
6. Can you explain the difference between synchronous and asynchronous code in Node.js?
Synchronous code is executed in a blocking manner, meaning that the next line of code will not be executed until the current line is finished. Asynchronous code is executed in a non-blocking manner, meaning that the next line of code will be executed even if the current line is not finished. This allows Node.js to handle multiple requests concurrently.
7. how to create microservices in node.js
To create microservices in Node.js, you can follow these steps:
– Set up a Node.js development environment. This includes installing Node.js and a code editor, such as Visual Studio Code.
– Choose a microservices framework. There are several options available for building microservices in Node.js, such as Express, Hapi, and NestJS. Each framework has its own set of features and capabilities, so you should choose the one that best fits your needs.
– Design your microservices architecture. Decide how you want to structure your microservices and what each service will be responsible for. It is also a good idea to think about how the services will communicate with each other and with any external dependencies.
– Implement your microservices. Start by creating a new Node.js project for each microservice, then implement the business logic and any necessary integrations.
– Test and deploy your microservices. Use automated testing tools to ensure that your microservices are working as expected, then deploy them to a cloud platform or on-premises infrastructure.
– Monitor and maintain your microservices. Use monitoring tools to keep track of the health and performance of your microservices, and make any necessary updates or adjustments as needed.
8. how to unit test node.js code
To unit test Node.js code, you can follow these steps:
– Choose a unit testing framework. There are several options available for unit testing Node.js code, such as Mocha, Jest, and Chai. Choose a framework that is well-supported and easy to use.
– Write your test cases. A test case is a function that tests a specific feature or behavior of your code. Your test cases should be designed to test individual units of code in isolation, without relying on external dependencies.
– Run your test cases. You can run your test cases using the command line or a testing tool, such as a continuous integration (CI) server.
– Analyze the test results. After running your test cases, you should receive feedback on which tests passed and which failed. If any tests failed, you can use this information to identify and fix any issues in your code.
– Repeat the process. As you make changes to your code, you should continue to write and run test cases to ensure that your code is functioning correctly.
It is also a good idea to follow best practices for unit testing, such as keeping your test cases small and focused, avoiding duplication, and testing for both expected and unexpected input.
9. What is Event loop in node.js
The event loop is a central part of the Node.js runtime that is responsible for handling asynchronous events and executing callback functions. It works by constantly checking for new events and placing them on a queue to be processed.
10. What are packages in node.js
A package in Node.js is a collection of modules that are bundled together and distributed via the npm (Node Package Manager) registry. npm is a tool that allows developers to easily install and manage packages in their projects.
11. Explain Asynchronous programming in node.js
Node.js uses an event-driven, non-blocking I/O model that makes it efficient for building scalable network applications. This means that instead of waiting for a blocking operation to complete before moving on to the next task, the Node.js runtime can continue processing other requests while the operation is being completed in the background.
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