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Node Js · Question Set
Testing & Deployment interview questions for placements and exams.
Questions
14
Included in this set
Subject
Node Js
Explore more sets
Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for Node Js.
Node.js apps can be deployed using PM2, Docker, or cloud platforms like AWS, Vercel, and Heroku. The process includes building the app, setting environment variables, and using a reverse proxy like Nginx for routing.
pm2 start app.js --name myapp pm2 logs myapp
For complete preparation, combine this set with full subject-wise practice for Node Js. You can also explore other subjects and sets from the links below.
You can wrap asynchronous code in a try-catch block or use middleware that automatically catches rejections. For production apps, centralized handlers prevent crashes and maintain clean logs.
try {
const data = await getData();
} catch (err) {
console.error('Error fetching data', err);
}Environment variables store secrets like API keys and database URLs. You can use `process.env` or a library like dotenv to load them from a .env file. Never hardcode secrets in code.
require('dotenv').config();
const dbUrl = process.env.DATABASE_URL;Mocha is a JavaScript test framework that runs in Node.js and browsers. Tests are written using describe/it blocks and assertions from Chai or Assert. Run with `npx mocha` or configure in npm scripts.
const assert=require('assert');
describe('Array',()=>{
it('should return -1 when value not found',()=>{
assert.equal([1,2,3].indexOf(4),-1);
});
});Jest provides zero-configuration testing with built-in mocks, snapshot testing, and parallel execution. It’s widely used for both backend and frontend testing in JavaScript projects.
test('adds 2 + 2',()=>{
expect(2+2).toBe(4);
});The Test Pyramid recommends writing many small unit tests, fewer integration tests, and very few end-to-end tests. For Node.js APIs, test each function (unit), routes with databases (integration), and full flows (E2E).
CI automatically runs tests and linting whenever you push code. Tools like GitHub Actions or Jenkins ensure consistent quality, catch bugs early, and simplify deployment pipelines.
PM2 manages Node.js processes, restarts apps on crashes, and supports cluster mode for multi-core scaling. It simplifies logging, monitoring, and zero-downtime deployments.
pm2 start app.js -i max pm2 monit
You can measure performance using tools like `clinic.js`, Node’s `--prof` flag, or APM tools (Datadog, New Relic). Benchmark code using console.time() or the Performance API to detect slow functions.
Static analysis tools like ESLint and TypeScript detect errors before runtime. They help enforce coding standards and reduce defects through early feedback during development.
Graceful shutdown ensures open connections and background tasks finish before exiting. You can listen for signals like SIGINT or SIGTERM and close servers cleanly.
process.on('SIGINT',()=>{
server.close(()=>{
console.log('Server closed gracefully');
process.exit(0);
});
});CI/CD automates testing, building, and deployment. CI ensures code integrity, while CD automates releases to production. Together, they reduce manual errors and accelerate delivery.
Logging helps track app behavior and diagnose problems. Libraries like Winston or Pino provide log levels (info, warn, error) and can output structured JSON for log management systems like Datadog or CloudWatch.
const winston = require('winston');
const logger = winston.createLogger({ level:'info', transports:[ new winston.transports.Console() ] });
logger.info('Server started');Node.js uses try-catch for synchronous errors and callback or Promise rejection handlers for async code. Uncaught errors crash the process, so using centralized error middleware or process event handlers (`process.on('uncaughtException')`) ensures graceful recovery.
app.use((err,req,res,next)=>{
console.error(err.stack);
res.status(500).send('Something broke!');
});