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

Transform supports binary data while Duplex supports only text

Answer

Duplex streams are faster; Transform streams include built-in error handling

Answer

There is no practical difference — they are fully interchangeable

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

The stream enters paused mode and waits for explicit read() calls

Answer

The stream buffers all data until the 'end' event fires

Answer

The stream switches to object mode

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

Check writable.buffer.length before each write call

Answer

Call writable.drain() to query available buffer capacity

Answer

Monitor the 'pressure' event emitted by the writable stream

Question 4

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

Accepted Answer

Buffer.concat([buf1, buf2])

Answer

buf1 + buf2

Answer

buf1.append(buf2)

Answer

Buffer.merge(buf1, buf2)

Question 5

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

Accepted Answer

readable.read(n)

Answer

readable.get(n)

Answer

readable.fetch(n)

Answer

readable.pull(n)

Question 6

What is a PassThrough stream in Node.js primarily used for?

Accepted Answer

A Transform implementation that passes data unchanged — useful for inspecting or measuring a pipeline

Answer

Routing data between two otherwise unconnected streams

Answer

Creating read-only snapshots of existing stream data

Answer

Compressing stream data transparently without altering the pipeline structure

Question 7

How do you determine the byte length of a string for a given encoding without allocating a full Buffer?

Accepted Answer

Buffer.byteLength(string, encoding)

Answer

string.byteLength

Answer

Buffer.sizeOf(string)

Answer

string.length (always equals byte length)