Node.js Streams & Buffers 3

Question 1

What is the primary difference between a Duplex stream and a Transform stream in Node.js?

Accepted Answer

Duplex has independent read and write sides; Transform derives its output directly from its input

Answer

A Duplex stream has completely independent read and write channels (like a TCP socket), while a Transform stream's readable output is produced by processing its writable input.

Question 2

What happens to a Readable stream when you attach a 'data' event listener to it?

Accepted Answer

The stream switches into flowing mode and data begins emitting automatically

Answer

Attaching a 'data' listener switches the stream from paused to flowing mode, causing chunks to be emitted as fast as they arrive without explicit pull calls.

Question 3

What is the correct way to detect backpressure when writing to a Writable stream?

Accepted Answer

Check if writable.write() returns false, then pause the source until the 'drain' event fires

Answer

writable.write() returns false when the internal buffer is full; you should pause the source and resume writing only after the 'drain' event is emitted.

Question 4

How do you efficiently concatenate multiple Buffer instances into a single Buffer?

Accepted Answer

Buffer.concat([buf1, buf2])

Answer

Buffer.concat() accepts an array of Buffers and an optional total length, allocating a new Buffer that contains all their bytes in sequence.

Question 5

How do you read exactly n bytes from a Readable stream operating in paused mode?

Accepted Answer

readable.read(n)

Answer

In paused mode, readable.read(n) pulls exactly n bytes from the internal buffer (or null if fewer are available), giving you precise control over how much data you consume.

Node.js Practice Test

Node.js Practice Test

Node.js Streams & Buffers 3