Node.js interview questions

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Node.js interview questions

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Question

Does Node.js provide built-in support for debugging?

Answer

Node7 introduced this new feature. It includes an out-of-process debugging utility accessible via a TCP-based protocol and built-in debugging client. To use it, start Node.js with the debug argument followed by the path to the script to debug. For example$ node debug YouAwesomeScript.jsThis command will show you a prompt indicating successful launch of debugger.

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Question

Why Node.js does not require multi threading to support parallel processing?

Answer

Node.js is single threaded and uses event loop to manage the processes. The asynchronous nature of Node.js results in non blocking handling of I/O, network or similar calls. These calls are usually blocking in other languages and require special threading to effectively make them work in parallel.

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Question

What is the difference between child_process.fork() and cluster.fork()?

Answer

Cluster allows TCP servers to be shared between workers whereas Child Process does not. Cluster.fork is implemented on top of child_process.fork. And in general you can say that Cluster wraps the functionality of Child_Process in a more useful way. Both are Node.js modules.

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Question

What is the difference between url.host and url.hostname?

Answer

Both methods get and set the hostname section of url. Url.hostname does not include the port. E.g

const myURL = new URL('https://sadiq.org:8080/hassaan');
console.log(myUrl.hostname) // sadig.org
console.log(myUrl.host) //sadiq.org:8080

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Question

Since Node.js runs on a single thread, how can a user take advantage of multi-core systems?

Answer

A single instance of Node.js runs in a single thread. To take advantage of multi-core systems, you can launch a cluster of Node.js processes to handle the load. The cluster module can create child processes which share server ports. You can import cluster like this. const cluster = require('cluster');Cluster have several useful methods like fork(), exit(), message(), isMaster(), isWorker() etc.

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Question

What is the difference between Buffer.alloc(size, fill) and Buffer.allocUnsafe(size).fill(fill)?

Answer

Buffer.alloc(size, fill) will never use the internal Buffer pool, while Buffer.allocUnsafe(size).fill(fill) will use the internal Buffer pool if size is less than or equal to half Buffer.poolSize. The difference is subtle but can be important when an application requires the additional performance that Buffer.allocUnsafe()provides.

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Question

Can we manage cryptography in Node.js without using external libraries?

Answer

To use the full grown cryptography in Node.js, you don’t need to use external libraries. You can use the crypto module of Node.js. It provides cipher, decipher, Diffie-Hellman key exchanges, Elliptic Curve Diffie-Hellman (ECDH) key exchanges and similar other methods to effectively manage cryptography. Also you can generate signatures using the Sign class of this module.

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