1. What is Node js ?
Node Js is one of the most popular and powerful server technologies today.
2. Explain CLI.
CLI stands for Command Line Interface. It is a utility or program on your computer where users type commands to perform some action or run some script rather than clicking on the screen.
3. Who is the author of Node Js ?
Node Js is written by Ryan Dahl.
5. Explain V8 Engine ?
6. What is NPM ?
7. How can you check the installed version of Node Js ?
Use node -v command to check the installed version of Node Js.
8. Explain ECMAScript ?
9. Explain Modules in Node Js ?
10. What are CommonJs Modules ?
11. Explain module.exports in Node Js ?
The method or variable defined in modules cannot be directly accessible by the outer world, that means you cannot call a module member from the external file. In order to access module member, we need to export the functions or variables of modules using module.exports method.
12. Is Node.js Single-threaded ?
Yes, Node Js is single threaded to perform asynchronous processing. Doing async processing on a single thread could provide more performance and scalability under typical web loads than the typical thread-based implementation.
13. What are events ?
An event is an action or occurrence recognized by software/app that is handled by event handler by writing a code that will be executed when the event fired.
14. Explain event loop in Node Js ?
In Node Js processes are single threaded, to supports concurrency it uses events and callbacks. An event loop is a mechanism that allows Node.js to perform non-blocking I/O operations.
15. Write the steps for setting up an Express JS application.
Following are the steps used to set up an express JS application: –
A folder with the same name as the project name is created.
A file named package.json is created inside the folder created.
“npm install” command is run on the command prompt. It installs all the libraries present in package.json.
A file named server.js is created.
“Router” file is created inside the package which consists of a folder named index.js.
“App” is created inside the package which has the index.html file.
16. What do you mean by Express JS?
17. What is the use of Express JS?
Express.js is a lightweight web application which helps in organizing the web application into MVC architecture on the server side.
Also Read:- Top 10 NodeJS Interview Questions and Answers
18. How can models be defined in Express JS?
There is no notion of any database in Express JS. So, the concept of models is left up to third-party node modules, allowing the users to interface with nearly any type of database.
19. How to authenticate users in express JS?
Since authentication is an opinionated area which is not ventured by express JS, therefore any authentication scheme can be used in express JS for the authentication of users.
20. Which template engine is supported by express JS?
Express JS supports any template engine that conforms to the (path, locals, callback) signature.
21. How can plain HTML be rendered in express JS?
There’s no need to render HTML with the res.render () function. If there’s a specific file, then you should use the res.sendFile () function. If any assets are being served from a dictionary, then express.static () middleware function needs to be used.
22. Explain what is libuv in Nodejs?
libuv is Cross-platform I/O abstraction library that supports asynchronous I/O based on event loops.It is written in C and released under MIT Licence.
libuv support Windows IOCP, epoll(4), kqueue(2), and Solaris event ports. Initially, it was designed for Node.js but later it is also used by other software projects.
23. What is JIT and how is it related to Node?
JIT stands for Just-in-time. A JIT compiler is a program which is used to send bytecode (it consists of instruction that can be interpreted) to the processor by converting it into instruction. After you have done with writing a program, the compiler compiles the source language statements into bytecode instead of compiling it into the code that carries the information which is similar to the specific hardware platform's processor.
24. How to use aggregation in Mongoose?
Aggregations are a set of functions that are used to manipulate the data that has been returned from a MongoDB query. In Mongoose, aggregations work as a pipeline. The aggregate function accepts the array of data transformations which are applied by data using different methods in terms of arguments.
25. How Node.js read the content of a file?
Normally NodeJs reads the content of a file in non-blocking, asynchronous way. Node Js uses its fs core API to deal with files. The easiest way to read the entire content of a file in nodeJs is with fs.readFile method. Below is sample code to read a file in NodeJs asynchronously and synchronously.
26. what is Closures?
A Closure is a function defined within another scope that has access to all the variables within the outer scope.
Global variables can be made local (private) with closures.
27. What are the features of Node.js?
28. 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 as opposed to the typical thread-based implementation.
29. Explain callback in Node.js.
A callback function is called at the completion of a given task. This 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.
30. Explain the role of REPL in Node.js.
31. What is the difference between Node.js and Ajax?
Ajax is primarily designed for dynamically updating a particular section of a page’s content, without having to update the entire page.
Node.js is used for developing client-server applications.
32. Explain chaining in Node.js.
Chaining is a mechanism whereby the output of one stream is connected to another stream creating a chain of multiple stream operations.
Also Read:- Top 20 NodeJS Interview Questions and Answers
33. What is the difference between AngularJS and Node.js?
Angular.JS is a web application development framework while Node.js is a runtime system.
34. Why is consistent style important and what tools can be used to assure it?
Consistent style helps team members modify projects easily without having to get used to a new style every time. Tools that can help include Standard and ESLint.
36. What is the fundamental difference between Node.js and Ajax?
37. Explain the term I/O in the context of Node.js.
I/O stands for input and output. It is used to access anything outside of the application. I/O gets loaded on to the machine memory in order to run programs after the application is fired up.
38. Which are the two types of API functions in Node.js?
Asynchronous, non-blocking functions and Synchronous, blocking functions.
39. Explain the role of the Callback function in Node.js.
In Node.js, the Callback function is used to cater to multiple requests made to the server. If there is a large file that is expected to take the server a long time to process, the Callback function can be invoked to ensure that other requests to the server are uninterrupted.
40. What is an error-first callback?
Error-first callbacks are essentially used to pass errors and data. By default, the first argument is always an error object, where the user needs to check if something is wrong.
41. Which is the framework that is most commonly used in Node.js?
The most commonly used Node.js framework is “Express”.
42. Define “event-driven programming.
It is essentially a programming paradigm where the program flow is characterized by events such as messages from other programs.
43. What are the two sections of event-driven programming?
Event Selection and Event Handling are two sections of event-driven programming.
44. Explain the Control Flow function.
It is a generic piece of code that runs concurrently between several asynchronous function calls.
45. List the steps involved in the Control Flow function.
Control the order of execution à Collect data à Limit concurrency à Call the next program step
46. Can a user access DOM in a Node?
No, you cannot access DOM.
47. In Node.js, which command is used to import external libraries?
A command called “require” is used for importing external libraries.
48. What is the biggest drawback of Node.js?
The biggest drawback is the fact that it is challenging to have one process with a single thread to scale up on multi core servers.
49. What is tracing?
This is the basic Node.js Interview Questions that are asked in an interview. Tracing enables you to trace information generated by V8. It can be enabled by passing flag as —
trace-events-enabled while starting the node. All these categories that are recorded can be specified by
the flag –trace-event-categories. The logs that are enabled can be opened as: chrome://tracing in Chrome.
50. Is Node A Single Threaded Application?
Yes! Node uses a single threaded model with event looping.
Also Read:- Top 30 NodeJS Interview Questions and Answers
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