Express js Interview Questions for Fresher and Experience
Express Interview Question
1. What is Express?
- Express.js is a web framework for Node.js that provides a robust set of features to develop web and mobile applications.
- It is used to design single-page, multi-page, and hybrid web applications.
- It supports the dynamic render HTML pages based on passing arguments.
- It allows the setup of middleware to respond to the HTTP request.
- It is used to define a routing table that is used to perform different actions based on the HTTP method and URL.
2. How to install Express using npm?
Commands to install the Express framework using NPM:
$ npm install express --save
3. What are the core features of Express?
- It can be used to design single-page, multi-page, and hybrid web applications.
- It allows the setup of middleware to respond to HTTP Requests.
- It defines a routing table that is used to perform different actions based on the HTTP method and URL.
- It allows to dynamically render HTML Pages based on passing arguments to templates.
4. What are HTTP methods?
- Routing refers to how an application's URLs respond to a user request.
- It can manage different types of HTTP requests.
- The route method is derived from the HTTP method.
- HTTP methods include GET, POST, PUT and DELETE.
5. What is GET Method?
The GET method is used to retrieve data. It requests a representation of the specified resource. GET is a common HTTP request used for building REST API. It is used to fetch data. Fetch data using GET Method in JSON format and paragraph format
6. What is POST Method?
The POST method is used to send large amounts of data because data is sent in the body. POST is a common HTTP request used for building REST API.
7. What is the PUT Method?
The PUT method is used for modification to an existing object identified by the URL.
8. What is DELETE Method?
The DELETE method is used to delete the specified resource.
9. What is Routing in Express?
- Routing refers to how an application's URLs respond to a user request.
- It can manage different types of HTTP requests.
- The function defines routes in an express application:
app.method(path,handler)
- the method here is any one of the HTTP verbs- get, put, post, and delete.
- the path is route.
- handler is call back function.
10. What is Middleware in Express?
Express.js Middleware functions are functions that have access to the response object(res), request object(req), and the next function in the request-response cycle. It appears in the middle between an initial request and the final intended route. It is used to perform tasks like body parsing for URL-encoded or JSON requests, cookie parsing or even building JavaScript modules on the fly.
11. What are the functions of Middleware?
Function or tasks of Middleware Function:
- Execute any code.
- Make changes to the request and the response objects.
- End the request-response cycle.
- Call the next middleware in the stack.
12. Name different types of Middleware
Types of Middleware
- Application-level middleware
- Router-level middleware
- Error-handling middleware
- Built-in middleware
- Third-party middleware
13. What is Application-level Middleware?
Application-level middleware is bound to an instance of the app object by using app.use() and app.method() functions here method is the HTTP method.
14. What is Router-level Middleware?
Router-level middleware is the same as application-level middleware except it is bound to an instance of express.Router().
15. What is Error-handling Middleware?
Error-handling middleware is the same as other middleware except the middleware function takes four arguments instead of three.
16. What is Built-in Middleware?
Built-in middleware functions are included with express. Built-in middleware functions present in Express are: express.static, express.json, and express.urlencoded.
17. Is Express.js a frontend or backend framework?
Express.js is a backend framework mainly designed to develop web applications and APIs. It comes in MEAN stack as a backend component.
18. What is MEAN stack?
MEAN stack where M stands for MongoDB, which handles the database; E stands for Express, which handles the backend; A stands for AngularJS, which is for the front-end, and N stands for Node.
19. Difference between Express and Node.
| Express | Node |
| Express.js is a web framework for Node.js that provides a robust set of features to develop web and mobile applications. | Node.js is an open-source platform used to execute javascript code |
| It is used to design single-page, multi-page, and hybrid web applications. | It is used to build server-side and event-driven apps. |
| Express is written in Javascript | It is written in c, c++and JavaScript |
| It is built on Node.js | It is built on Google's V8 engine. |
| It is easy to code and requires less time | It requires complex coding |
20. Mention the arguments in the Express JS route handler function.
The arguments that are available in the route handler function of Express JS are given below:
- Res - It is the response object.
- Req - It is the request object
- Next (optional) - This argument is used for passing the management to any of the above-given route handlers.
