Express JS interview Questions Series: Part1

2 min readJun 7, 2023

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Question 1: What is Express.js and what are its key features?

Answer: Express.js is a popular web application framework for Node.js. It provides a minimalistic and flexible set of features for building web applications and APIs. Some key features of Express.js include routing, middleware support, template engine integration, and simplified handling of HTTP requests and responses.

Question 2: How do you create a basic Express.js application?

Answer: To create a basic Express.js application, you need to install Express.js using npm and then create an instance of the Express application.

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// Import the Express module
const express = require('express');

// Create an instance of Express application
const app = express();// Start the server
app.listen(3000, () => {
  console.log('Server is running on port 3000');
});

Question 3: How do you define routes in Express.js?

Answer: In Express.js, routes are defined using the app.get(), app.post(), app.put(), app.delete(), or app.use() methods. Here's an example of defining a GET route:

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app.get('/users', (req, res) => {
  res.send('Get all users');
});

Question 4: How do you handle URL parameters in Express.js?

Answer: URL parameters can be accessed using req.params. Here's an example:

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app.get('/users/:id', (req, res) => {
  const userId = req.params.id;
  res.send(`User ID: ${userId}`);
});

Question 5: What is middleware in Express.js and how is it used?

Answer: Middleware functions in Express.js are functions that have access to the req, res, and next objects. They can modify request and response objects, execute code, and invoke the next middleware function in the stack. Middleware is used for tasks such as logging, authentication, error handling, etc. Here's an example:

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// Middleware function
const logger = (req, res, next) => {
  console.log(`Request URL: ${req.url}`);
  next();
};

// Register middleware
app.use(logger);

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Express JS interview Questions Series: Part1

Written by Tasadduq Ali