Do you dream of becoming a software engineer or, more particularly, a Node JS Developer? Are you going to appear for the interview soon? Does the thought of Express JS Interview Questions bother you? Then take a moment and relax! In this article, we will provide you with Express JS Interview Questions having a high probability of getting asked. Make sure to check them out at least once before your interview.
Express JS is a flexible and back-end web application Node JS framework with a powerful set of web and mobile application features. It was released as open-source software licensed under MIT in 2010. We can design single-page, multi-page, and hybrid web applications as well as APIs with the Express JS framework. It is built over Node JS, helping manage routes and servers. And it has been conferred the title of standard server framework for Node JS. It provides several HTTP utility methods to the user for creating APIs and apps easily.
Have a look at the following Express JS facts before moving forward:
We have categorized Express JS Interview Questions - 2023 (Updated) into 3 levels they are:
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Express application generator is used for quickly creating an application skeleton. The given command is used for installing the express application generator.
npm install expr
ess-generator –g
express myApp
It will create the project "myApp" with some files. Then we install all the dependencies stated in package.json using the given command:
cd myApp
npm install
Generators are used by yeoman for scaffolding the applications. And we can use the following command to install yeoman.
npm install –g yeoman
The arguments that are available in the route handler function of Express JS are given below:
[ Learn Complete Express JS Tutorial ]
Debugging on Windows can be done as follows:
set DEBUG = express:*
node app.js
And debugging on Linux can be done as follows:
DEBUG = express:*
node app.js
Express JS provides the following built-in middleware functions:
Some of the many third-party middlewares that the Express JS provides are:
We use the application-level Middleware for binding the app object with the help of the app.use() method. It can be applied on all routes. The syntax is given below:
// This Middleware executes for each route.
App.use(function (req, res, next) {
console.log(‘Current Time:’, Date.now())
next()
})
Router-level Middleware - We use the router-level Middleware for binding with a particular instance of Express.Router().
Built-in Middleware - The version 4.x of Express introduced the built-in Middleware. The dependency on connecting gets removed by use of this Middleware.
A myriad of NoSQL and RDBMS databases are supported by Express JS, such as:
Related Article MongoDB vs PostgreSQL |
CORS is the acronym for Cross-origin resource sharing. We can request the restricted resources from another server or domain using this mechanism. And we can do this mainly in the following three ways:
Express JS provides us with two ways for configuring the properties, which are given below:
The properties are configured by the given steps:
The properties are configured by the given steps:
There is no specific answer to this question. The dimensions of our application and hence the concerned team define the solution in different situations. The express logic in the Routes and alternative applications can board as many files as we want in any directory structure. The given examples can be read for further inspiration:
We don’t need to render HTML with the function- res.render(). Instead, we can use the res.sendFile() function if we have a specific file. And we can use the Express.static() middleware function if we serve several assets from a directory.
Create a new file by the name- index.js and type the following commands:
var express = require (‘express’);
var app = express ();
app.get (‘/’, function (req, res){
res.send (“Hello world”);
});
app.listen (3000);
Now go to the terminal after saving it and type:
nodemon index.js
The following HTTP methods are the most used ones:
We use the “res.cookie(‘username’, ‘Flavio’)” command is used for manipulating. But it accepts a third parameter conaining various options as specified below:
res.cookie (‘username’, ‘Flavio’, { domain: ‘flaviocopes.com’, path: ‘/administrator’, secure: true })
res.cookie (‘username’, ‘Flavio’ , { expires: new Date(Date.now() + 90000), httpOnly: true})
A cross-Origin can fail in the following scenarios-
We will first install it using the given command:
npm install pug
Then we will set it as following when initializing the Express app:
const express = require ('express')
const app = express()
app.set ('view engine', 'pug')
People can always enter weird things via the client-side code. They use the tools to POST things directly to our endpoints. For this, the Express provides various sanitizing methods to prevent these happenings.
Consider the following sanitizing methods:
Consider the given example of HTML form code that allows a user to upload file.
<form method = “POST” action = “/submit-form”>
<input type = “file” name = “document” />
<input type = “submit” />
</form>
We can call the following methods in such cases-
We will follow the given steps to set up HTTP:
The options available are given below:
Related Article Basic Examples of Node JS |
The event-loop manages the async content using a listener and queue. The main thread sends the async function to a different thread whenever it requires to be executed. Alongside, v8 is allowed to execute the main code. The event loop has different stages including pending callbacks, timers, check, poll, close callbacks, etc. with different FIFO queues.
The server initializes the Middleware, routes, and other application logic. On the other hand, the app contains all the business logic that the server-initiated routes will serve. This enables the encapsulation of the business logic from the application logic for smooth functioning.
Check out Node JS Interview Questions and Answers |
It's a class of Node JS capable of emitting events. We do this by attaching the named events emitted by the object by using the function- eventEmitter.on().
Cluster:
Worker Threads:
Let's go through the top 10 Frequently Asked Express JS Interview Questions and Answers (FAQs)
The following major companies use Express JS-
React JS, Meteor, Mean, Flask, Catalyst, Django, Apache Flex, and Laravel are some of the popular alternatives to Express JS.
Some distinct features of Express JS are given below-
The following popular tools integrate with Express JS:
Express JS is a back-end framework built on JavaScript. It is the MEAN stack's back-end component. Here, 'M' refers to MongoDB, and it manages the database. 'E' refers to Express, and it manages the back-end. 'A' refers to AngularJS, and it handles the back-end. And 'N' refers to Node.
Node JS is an open-source platform on which the JavaScript code is executed outside of a browser. It is used by several companies, including Uber, Walmart, Netflix, etc. It is a platform acting as a web server and not a programming language or framework. On the other hand, Express JS is a framework built on Node JS.
All template engines following the locals, path, and callback signatures are supported by Express JS.
Middleware is the function that we invoke before the final request process through the express routing layer. Its functions are given below:
The main types of Middleware are given below:
The process of creating the structure of the application is referred to as scaffolding. The two ways of achieving it are given below:
Node JS along with Express JS, allows building a complex and high-level web application from a single line of code easily. That's why it is one of the most sought-after skills in the industry today. And this was a comprehensive list of Express JS Interview Questions that are often asked in interviews. We hope that it will be beneficial for your scheduled interview in the near future.
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Madhuri is a Senior Content Creator at MindMajix. She has written about a range of different topics on various technologies, which include, Splunk, Tensorflow, Selenium, and CEH. She spends most of her time researching on technology, and startups. Connect with her via LinkedIn and Twitter .
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