1. What is Node.js?
Node.js is Server-side scripting which is used to build scalable programs. It is a web application framework built on Google Chrome’s JavaScript Engine. It runs within the Node.js runtime on Mac OS, Windows, and Linux with no changes. This runtime facilitates you to execute a JavaScript code on any machine outside a browser.
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. What is the purpose of Node.js?
These are the following purposes of Node.js:
Real-time web applications
Network applications
Distributed systems
General purpose applications
3. Where is Node.js used?
Node.js is used in a variety of domains. But, it is very well regarded in the design of the following concepts:
Network application
Distributed computing
Responsive web apps
Server–Client applications
4. What is NPM?
Javascript operates in a runtime environment with the help of node js having its own package manager, this package manager is called NPM.
5. What is CLI in Node.js?
One of the vital reasons for Node.js getting popular is its 900000 packages connected to a large ecosystem. CLI is a command-line interface that will allow you to automate your tasks by taking advantage of this vast ecosystem. Not only that, by writing CLI you can differentiate your proposed packages among the ecosystem.
6. 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.
7. 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.
8. In which Language Node Js is written?
Node.js shows compatibility with three types of language
C
C++
Javascript
9. What is a Javascript Engine?
Javascript engine is used to run the java code in the browser so you can define a javascript engine as a computer program that is used to perform the java code. Initially, it was just used for interpretation and progressively it improved and got evolved. Generally, all browsers have one dealer and he is the one who develops the javascript engine.
10. What is a V8 Engine?
In 2008 when google chrome was launched time chrome also introduced its project of the V8 engine. It is an open-source network that can be written in the c++ language.
11. What is ECMAScript?
Ecmascript first appeared in 1997, which was specified and developed by Esma internationals. Evmascriot is also a programming language, which developed various other scripts like Jscript, ActionScript, and the most popularly used javascript.
12. Explain Node.js web application architecture?
A web application distinguishes into 4 layers:
- Client Layer: The Client layer contains web browsers, mobile browsers or applications which can make an HTTP request to the web server.
- Server Layer: The Server layer contains the Web server which can intercept the request made by clients and pass them the response.
- 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.
- Data Layer: The Data layer contains databases or any source of data.
13. What is control flow function?
A generic piece of code which runs in between several asynchronous function calls is known as control flow function.
14. Explain the steps how “Control Flow” controls the functions calls?
- Control the order of execution
- Collect data
- Limit concurrency
- Call the next step in program
15. Is Node.js is single threaded?
Yes, Node.js is single threaded. For async processing, Node.js was created explicitly as an experiment. It is believed that more performance and scalability can be achieved by doing async processing on a single thread under typical web loads than the typical thread based implementation.
16. If Node.js is single-threaded, then how does it handle concurrency?
The Multi-Threaded Request/Response Stateless Model is not followed by the Node JS Platform, and it adheres to the Single-Threaded Event Loop Model. The Node JS Processing paradigm is heavily influenced by the JavaScript Event-based model and the JavaScript callback system. As a result, Node.js can easily manage more concurrent client requests. The event loop is the processing model’s beating heart in Node.js.
17. 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.
18. What are the advantages of using promises instead of callbacks?
- The control flow of asynchronous logic is more specified and structured.
- The coupling is low.
- We’ve built-in error handling.
- Improved readability.
19. How is Node.js most frequently used?
Node.js is widely used in the following applications:
- Real-time chats
- Internet of Things
- Complex SPAs (Single-Page Applications)
- Real-time collaboration tools
- Streaming applications
- Microservices architecture
20. Why is Node.js preferred over other backend technologies like Java and PHP?
Some of the reasons why Node.js is preferred include:
- Node.js is very fast
- Node Package Manager has over 50,000 bundles available at the developer’s disposal
- Perfect for data-intensive, real-time web applications, as Node.js never waits for an API to return data
- Better synchronization of code between server and client due to same code base
- Easy for web developers to start using Node.js in their projects as it is a JavaScript library
21. Which database is more popularly used with Node.js?
MongoDB is the most common database used with Node.js. It is a NoSQL, cross-platform, document-oriented database that provides high performance, high availability, and easy scalability.
22. What are some of the most commonly used libraries in Node.js?
There are two commonly used libraries in Node.js:
ExpressJS – Express is a flexible Node.js web application framework that provides a wide set of features to develop web and mobile applications.
Mongoose – Mongoose is also a Node.js web application framework that makes it easy to connect an application to a database.
23. What do you understand by callback hell in Node.js?
Callback hell is a phenomenon that creates a lot of problems for a JavaScript developer when he tries to execute multiple asynchronous operations one after the other. A function is called an asynchronous function when some external activity must complete before processing a result. It is called asynchronous because there is an unpredictable amount of time before a result becomes available. These functions require a callback function to handle errors and process the result.
getData(function(a){
getMoreData(a, function(b){
getMoreData(b, function(c){
getMoreData(c, function(d){
getMoreData(d, function(e){
...
});
});
});
});
});
24. What are some commonly used timing features of Node.js?
Following is a list of some commonly used timing features of Node.js:
setTimeout/clearTimeout: This timing feature of Node.js is used to implement delays in the code execution.
setInterval/clearInterval: The setInterval or clearInterval timing feature is used to run a code block multiple times in the application.
setImmediate/clearImmediate: This timing feature of Node.js is used to set the execution of the code at the end of the event loop cycle.
nextTick: This timing feature sets the execution of code at the beginning of the next event loop cycle.
25. Give an example to demonstrate how can we use async await in Node.js?
See the following example of using async-await pattern:
function wait (timeout) {
return new Promise((resolve) => {
setTimeout(() => {
resolve()
}, timeout);
});
}
async function requestWithRetry (url) {
const MAX_RETRIES = 10;
for (let i = 0; i <= MAX_RETRIES; i++) {
try {
return await request(url);
}
catch (err) {
const timeout = Math.pow(2, i);
console.log('Waiting', timeout, 'ms');
await wait(timeout);
console.log('Retrying', err.message, i);
}
}
}