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Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It is an open-source software designed to simplify the process of building complex websites by providing a simple interface for creating server-side rendered pages, APIs, and connecting to databases. Express.js facilitates rapid development by offering numerous features like template engines, simplified multiple routing, database integration, etc. It also allows developers to build software with JavaScript on the server side in an asynchronous manner which can improve performance. Express.js forms part of the MEAN (MongoDB, ExpressJS, AngularJS and NodeJS) stack - a full-stack JavaScript solution that helps you build fast and maintainable web applications.

Ask the right questions secure the right Express.js framework for Node.js talent among an increasingly shrinking pool of talent.

First 20 minutes

General Express.js framework for Node.js app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Express.js framework for Node.js application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you install Express.js?

You can install Express.js by using the Node Package Manager (npm). The command is 'npm install express'.

What are the core features of Express.js?

Express.js has several core features including middleware, template engines, simplified multiple routing, database integration, and it supports many plugins.

How would you create a basic route in Express.js?

You can create a basic route in Express.js using the app.get() or app.post() methods. For example, 'app.get('/', function(req, res){ res.send('Hello World'); });'.

What is middleware in the context of Express.js?

Middleware are functions that have access to the request object (req), the response object (res), and the next middleware function in the application’s request-response cycle.

How would you serve static files in Express.js?

You can serve static files in Express.js using the express.static built-in middleware function. For example, 'app.use(express.static('public'))' would serve static files from the 'public' directory.

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What you’re looking for early on

Does the candidate have a solid understanding of Express.js?

Can they demonstrate experience with Node.js?

Are they able to articulate how they have used Express.js in past projects?

Do they have knowledge of other technologies that are commonly used with Express.js, like MongoDB and AngularJS?

Next 20 minutes

Specific Express.js framework for Node.js development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

What are the differences between Express.js and Hapi.js?

Express.js is more flexible and has a larger community, while Hapi.js is more configurable and has built-in support for input validation, caching, and authentication.

How would you handle errors in Express.js?

You can handle errors in Express.js by defining error-handling middleware functions. These functions have four arguments instead of three: (err, req, res, next).

What is the purpose of app.use() in Express.js?

app.use() is used to mount the specified middleware function or functions at the specified path. If path is not specified, it defaults to '/'.

How would you implement authentication in Express.js?

You can implement authentication in Express.js using middleware like Passport.js, which can be easily integrated with Express.js and supports various authentication mechanisms.

What is the difference between app.get() and app.route() in Express.js?

app.get() is used to handle GET requests at a specific route, while app.route() is used to chain route handlers for a specific route.

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At this point, a skilled Express.js framework for Node.js engineer should demonstrate strong problem-solving abilities, proficiency in Express.js framework for Node.js programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Express.js framework for Node.js.

What does the following Express.js code do?
const express = require('express');
const app = express();
app.get('/', function(req, res){
  res.send('Hello World!');
});
app.listen(3000);
This code starts a simple Express.js server that listens on port 3000. When a GET request is made to the root URL ('/'), it responds with 'Hello World!'.
What will be the output of the following Express.js middleware code?
const express = require('express');
const app = express();
app.use(function(req, res, next) {
  console.log('Time:', Date.now());
  next();
});
This code sets up middleware for the Express.js application that logs the current time to the console whenever a request is received. It does not produce an output, but modifies the behavior of the server.
What does the following Express.js code do related to array or collection manipulation?
app.get('/users/:userId/books/:bookId', function (req, res) {
  res.send(req.params)
})
This code sets up a route handler for GET requests made to '/users/:userId/books/:bookId'. It responds by sending back the route parameters (in this case, 'userId' and 'bookId') as an object.
What does the following Express.js code do related to threading or concurrency?
app.get('/long-process', function (req, res) {
  setImmediate(() => {
    // long running process here
  });
  res.send('Process started');
});
This code sets up a route handler for GET requests made to '/long-process'. It starts a long running process in a non-blocking way using setImmediate, and immediately responds with 'Process started'. This allows the server to handle other requests concurrently, without waiting for the long process to complete.

Wrap-up questions

Final candidate for Express.js framework for Node.js Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Express.js framework for Node.js application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

How would you handle file uploads in Express.js?

You can handle file uploads in Express.js using middleware like Multer. Multer adds a body object and a file or files object to the request object.

What is the difference between res.send() and res.json() in Express.js?

res.send() sends a response of various types, while res.json() sends a JSON response. res.json() also converts non-objects into valid JSON.

How would you implement session management in Express.js?

You can implement session management in Express.js using middleware like express-session. This middleware stores session data on the server and attaches a session ID to the client's cookie.

Express.js framework for Node.js application related

Product Perfect's Express.js framework for Node.js development capabilities

Beyond hiring for your Express.js framework for Node.js engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Express.js framework for Node.js projects, and can engage in multiple capacities.

Express.js framework for Node.js Consultive assessments

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Custom Express.js framework for Node.js development projects

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Hiring guide for Express.js framework for Node.js Engineers

Express.js framework for Node.js Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Express.js framework for Node.js engineer at this point.

Express.js framework for Node.js Consultive assessments

Custom Express.js framework for Node.js development projects