Which Express JS Interview questions to prepare for practice?

Express.js Questions to Prepare for Practice

Practicing Express.js questions helps in mastering the core concepts, APIs, and real-world problem-solving skills associated with building server-side applications. Below is a categorized list of questions for effective preparation.

1. Basics of Express.js

• What is Express.js, and why is it used in Node.js?

• How do you create a simple Express server that listens on port 3000?

  const express = require("express");
  const app = express();
  
  app.get("/", (req, res) => {
    res.send("Hello, World!");
  });
  
  app.listen(3000, () => {
    console.log("Server running on port 3000");
  });

• What are the main features of Express.js?

• How does Express.js differ from Node.js?

2. Routing in Express.js

• How do you define routes in Express.js?

• Write an example of route parameters in Express.js.

  app.get("/user/:id", (req, res) => {
    res.send(`User ID: ${req.params.id}`);
  });

• How can you define middleware for specific routes?

• What is the difference between app.use() and app.get()?

3. Middleware in Express.js

• What is middleware in Express.js, and how is it used?

• How do you create and use custom middleware?

  const logger = (req, res, next) => {
    console.log(`${req.method} ${req.url}`);
    next();
  };
  
  app.use(logger);

• What is the difference between application-level and router-level middleware?

• How can you handle errors using middleware?

4. Request and Response Handling

• How do you access query parameters in an Express route?

  app.get("/search", (req, res) => {
    res.send(`Search query: ${req.query.q}`);
  });

• How do you send JSON responses in Express.js?

• Write an example of handling file uploads in Express.js.

5. Express.js with Databases

• How do you connect Express.js with MongoDB?

  const mongoose = require("mongoose");
  
  mongoose.connect("mongodb://localhost:27017/mydb", { useNewUrlParser: true });
  
  app.get("/data", async (req, res) => {
    const data = await MyModel.find();
    res.json(data);
  });

• How do you perform CRUD operations in Express.js with a database?

• What are the best practices for structuring database logic in an Express application?