Writing data with Writable streams in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Writable stream in Node.js?

A Writable stream is an abstraction in Node.js that allows you to write data piece by piece to a destination, like a file or network socket, without loading everything into memory at once.

beginner

How do you create a Writable stream to write to a file?

You use the fs module's createWriteStream method, like: <code>const fs = require('fs'); const stream = fs.createWriteStream('file.txt');</code> This stream lets you write data to 'file.txt' efficiently.

beginner

What method do you use to write data to a Writable stream?

You use the write() method, passing the data you want to write. For example: stream.write('Hello'); writes 'Hello' to the stream.

intermediate

Why should you listen for the 'drain' event when writing to a Writable stream?

Because write() returns false if the internal buffer is full. The 'drain' event tells you when it's safe to write more data without overloading memory.

beginner

How do you properly close a Writable stream after writing data?

You call the end() method on the stream. This signals that no more data will be written and lets the stream finish writing any buffered data.

Which method starts writing data to a Writable stream in Node.js?

A pipe()

B read()

C write()

D open()

The write() method is used to send data to a Writable stream.

What does the write() method return if the internal buffer is full?

A true

B undefined

C null

D false

write() returns false when the buffer is full, signaling you should wait before writing more.

Which event should you listen to before resuming writing after a false return from write()?

A drain

B error

C finish

D close

The 'drain' event indicates the buffer has emptied and you can write again.

How do you signal that you have finished writing data to a Writable stream?

A close()

B end()

C finish()

D destroy()

Calling end() tells the stream no more data will be written.

Which Node.js module provides the createWriteStream method?

A fs

B stream

C net

D http

The fs module provides createWriteStream to write files.

Explain how to write data to a file using a Writable stream in Node.js.

Think about creating the stream, writing data, handling buffer limits, and closing.

Describe why handling the 'drain' event is important when writing large amounts of data.

Consider what happens when the stream's internal buffer fills up.