Today I come up with some of the frequently asked NodeJS Interview questions and answers for beginners which help them to crack the interview. Let's have a look.
Beginner Node.js Interview Questions
1. What is Node.js? Where can you use it?
Node.js is an open-source, cross-platform JavaScript runtime environment and library to run web applications outside the client’s browser. It is used to create server-side web applications.
Node.js is perfect for data-intensive applications as it uses an asynchronous, event-driven model. You can use I/O intensive web applications like video streaming sites. You can also use it for developing: Real-time web applications, Network applications, General-purpose applications, and Distributed systems.
2. Why use Node.js?
Node.js makes building scalable network programs easy. Some of its advantages include:
It is generally fast It rarely blocks It offers a unified programming language and data type Everything is asynchronous It yields great concurrency
3. What is the first-class function in Javascript?
When functions can be treated like any other variable then those functions are first-class functions. There are many other programming languages, for example, scala, Haskell, etc which follow this including JS. Now because of this function can be passed as a param to another function(callback) or a function can return another function(higher-order function). map() and filter() are higher-order functions that are popularly used.
4. What is Node.js and how it works?
Node.js is a virtual machine that uses JavaScript as its scripting language and runs Chrome’s V8 JavaScript engine. Basically, Node.js is based on an event-driven architecture where I/O runs asynchronously making it lightweight and efficient. It is being used in developing desktop applications as well with a popular framework called electron as it provides API to access OS-level features such as file system, network, etc.
5. How do you manage packages in your node.js project?
It can be managed by a number of package installers and their configuration file accordingly. Out of them mostly use npm or yarn. Both provide almost all libraries of javascript with extended features of controlling environment-specific configurations. To maintain versions of libs being installed in a project we use package.json and package-lock.json so that there is no issue in porting that app to a different environment.
6. How is Node.js better than other frameworks most popularly used?
Node.js provides simplicity in development because of its non-blocking I/O and even-based model results in short response time and concurrent processing, unlike other frameworks where developers have to use thread management.
It runs on a chrome v8 engine which is written in c++ and is highly performant with constant improvement.
Also since we will use Javascript in both the frontend and backend the development will be much faster.
And at last, there are ample libraries so that we don’t need to reinvent the wheel.
7. Explain the steps of how “Control Flow” controls the functions calls?
Control the order of execution Collect data Limit concurrency Call the following step in the program.
8. What are some commonly used timing features of Node.js?
setTimeout/clearTimeout – This is used to implement delays in code execution. setInterval/clearInterval – This is used to run a code block multiple times. setImmediate/clear immediate – This is used to set the execution of the code at the end of the event loop cycle. process.nextTick – This is used to set the execution of code at the beginning of the next event loop cycle.
9. What are the advantages of using promises instead of callbacks?
The main advantage of using promise is you get an object to decide the action that needs to be taken after the async task completes. This gives more manageable code and avoids callback hell.
10. What is a fork in node JS?
A fork in general is used to spawn child processes. In node, it is used to create a new instance of the v8 engine to run multiple workers to execute the code.
11. Why is Node.js single-threaded?
Node.js was created explicitly as an experiment in async processing. This was to try a new theory of doing async processing on a single thread over the existing thread-based implementation of scaling via different frameworks.
12. Why is Node.js Single-threaded?
Node.js is single-threaded for async processing. By doing async processing on a single thread under typical web loads, more performance and scalability can be achieved instead of the typical thread-based implementation.
13. Explain callback in Node.js.
A callback function is called after a given task. It allows other code to be run in the meantime and prevents any blocking. Being an asynchronous platform, Node.js heavily relies on callback. All APIs of Node are written to support callbacks.
14. What is the difference between Asynchronous and Non-blocking?
Asynchronous literally means not synchronous. We are making HTTP requests which are asynchronous, which means we are not waiting for the server response. We continue with other block and respond to the server response when we received. The term Non-Blocking is widely used with IO. For example, non-blocking read/write calls return with whatever they can do and expect the caller to execute the call again. The read will wait until it has some data and put the calling thread to sleep.
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