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Node Js · Question Set
Core Node Internals interview questions for placements and exams.
Questions
11
Included in this set
Subject
Node Js
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for Node Js.
REPL stands for Read–Eval–Print–Loop. It is an interactive shell that executes JavaScript code line by line. It helps developers test and debug quickly. • Read – reads user input • Eval – evaluates input • Print – outputs result • Loop – waits for new input again.
node > let x = 10; x * 2 20
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.
WebSockets enable full-duplex (two-way) communication between client and server. They maintain an open connection for real-time updates (e.g., chats, games). Implemented using `ws` or `socket.io` libraries.
const WebSocket=require('ws');
const wss=new WebSocket.Server({port:8080});
wss.on('connection',ws=>ws.send('Connected!'));CORS (Cross-Origin Resource Sharing) enables web apps running on one domain to access resources from another. The `cors` npm package sets headers to allow or restrict requests from other origins.
const cors=require('cors');
app.use(cors({origin:'*'}));The Timers module allows scheduling of code execution after a specified time. It provides functions like `setTimeout()`, `setInterval()`, and `setImmediate()` to run callbacks asynchronously in future event loop phases.
setTimeout(()=>console.log('After delay'),1000);
setImmediate(()=>console.log('Next phase'));Buffers handle raw binary data in Node.js. They are useful when dealing with file streams, TCP packets, or image data. Buffers are fixed-size byte arrays allocated outside the V8 heap for efficient memory handling.
const buf = Buffer.from('Hello');
console.log(buf.toString());The util module provides helpful functions for debugging and inheritance. Common methods include `util.inherits()` for classical inheritance, `util.promisify()` to convert callbacks into Promises, and `util.format()` for string formatting.
const util=require('util');
const wait=util.promisify(setTimeout);
await wait(1000);Control flow refers to managing asynchronous operations’ order and results. Since Node.js doesn’t block execution, control flow ensures callbacks, promises, and async/await handle dependencies correctly in async code.
The Redis module allows connecting to Redis servers for caching, message brokering, and session storage. It improves response speed by storing frequent queries in memory instead of querying the database repeatedly.
const redis=require('redis');
const client=redis.createClient();
client.set('user','John');The TLS module provides SSL/TLS protocols for encrypting data over the network. It’s built on OpenSSL and ensures secure communication between clients and servers.
const tls=require('tls');
const server=tls.createServer({key,cert},()=>console.log('TLS Active'));You can use the global `process.argv` array to read CLI arguments passed to the script. Arguments start from index 2, as the first two are node executable and script path.
console.log(process.argv.slice(2)); // node app.js arg1 arg2
The DNS (Domain Name System) module provides methods to resolve domain names to IP addresses. It can perform both asynchronous lookups and direct OS-level resolution using `dns.lookup()` and `dns.resolve()`.
const dns=require('dns');
dns.lookup('google.com',(err,addr)=>console.log(addr));