Virtusa Node.js Interview Questions
1. How is Node.js better than other frameworks most popularly used?
Nodejs is better than other frameworks in following ways:
1) 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.
2) It runs on a chrome v8 engine which is written in c++ and is highly performant with constant improvement.
3) Also since we will use Javascript in both the frontend and backend the development will be much faster.
4) And at last, there are ample libraries so that we don’t need to reinvent the wheel.
2. 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.
3. Explain Node.js web application architecture?
A web application distinguishes into 4 layers:
1) Client Layer: The Client layer contains web browsers, mobile browsers or applications which can make an HTTP request to the web server.
2) Server Layer: The Server layer contains the Web server which can intercept the request made by clients and pass them the response.
3) Business Layer: The business layer contains application server which is utilized by the web server to do required processing. This layer interacts with the data layer via database or some external programs.
4) Data Layer: The Data layer contains databases or any source of data.
4. How can you manage the packages in your Node.js project?
We can manage the packages in our Node.js project by using several package installers and their configuration file accordingly. Most of them use npm or yarn. The npm and yarn both provide almost all libraries of JavaScript with extended features of controlling environment-specific configurations. We can use package.json and package-lock.json to maintain versions of libs being installed in a project. So, there is no issue in porting that app to a different environment.
5. What do you understand by the term fork in Node.js?
Generally, a fork is used to spawn child processes. In Node.js, it is used to create a new instance of the V8 engine to run multiple workers to execute the code.
6. What are buffers in Node.js?
In general, a buffer is a temporary memory mainly used by the stream to hold on to some data until it is consumed. Buffers are used to represent a fixed-size chunk of memory allocated outside of the V8 JavaScript engine. It can't be resized. It is like an array of integers, which each represents a byte of data. It is implemented by the Node. js Buffer class. Buffers also support legacy encodings like ASCII, utf-8, etc.
7. How can you avoid callbacks?
To avoid callbacks, you can use any one of the following options:
- You can use modularization. It breaks callbacks into independent functions.
- You can use promises.
- You can use yield with Generators and Promises.
8. Explain the tasks of terms used in Node REPL.
Following are the terms used in REPL with their defined tasks:
Read: It reads user's input; parse the input into JavaScript data-structure and stores in memory.
Eval: It takes and evaluates the data structure.
Print: It is used to print the result.
Loop: It loops the above command until user press ctrl-c twice to terminate.
9. What is npm? What is the main functionality of npm?
npm stands for Node Package Manager. Following are the two main functionalities of npm:
- Online repositories for node.js packages/modules which are searchable on search.nodejs.org
- Command line utility to install packages, do version management and dependency management of Node.js packages.
10. What is the use of a buffer class in Node.js?
The Node.js provides Buffer class to store raw data similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap. It is a global class and can be accessed in an application without importing a buffer module. Buffer class is used because pure JavaScript is not compatible with binary data. So, when dealing with TCP streams or the file system, it's necessary to handle octet streams.
11. What is the difference between readFile and createReadStream in Node.js?
In Node.js, there are two ways to read and execute files: readFile and CreateStream.
- The readFile() process is a fully buffered process that returns the response only when the complete file is pushed into the buffer and is read. This process is called a memory-intensive process, and in the case of large files, the processing can be very slow.
- On the other hand, the createReadStream() is a partially buffered process that treats the entire process as an event series. The entire file is split into chunks and then processed and sent back as a response one by one. After completing this step, they are finally removed from the buffer. Unlike the readFile process, the createReadStream process is effective for the processing of large files.
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