Stream types (Readable, Writable, Transform, Duplex) in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a readable stream from a string.

Node.js

const { Readable } = require('stream');
const readable = [1] Readable({
  read() {
    this.push('Hello');
    this.push(null);
  }
});

Drag options to blanks, or click blank then click option'

Acreate

Bnew

Cfrom

Dpipe

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'from' expects an iterable argument, not an options object with read().

Trying to use 'pipe' here is incorrect.

The new Readable() constructor creates a readable stream instance where you can define a custom read() method to push data like strings.

2fill in blank

medium

Complete the code to write data to a writable stream.

Node.js

const { Writable } = require('stream');
const writable = new Writable({
  write(chunk, encoding, callback) {
    console.log(chunk.toString());
    [1]();
  }
});

Drag options to blanks, or click blank then click option'

Aend

Bwrite

Ccallback

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'write' inside 'write' causes infinite recursion.

Forgetting to call 'callback' causes the stream to hang.

The write method must call the callback function to signal that it finished processing the chunk.

3fill in blank

hard

Fix the error in the transform stream by completing the missing method call.

Node.js

const { Transform } = require('stream');
const transform = new Transform({
  transform(chunk, encoding, callback) {
    this.push(chunk.toString().toUpperCase());
    [1]();
  }
});

Drag options to blanks, or click blank then click option'

Apush

Bend

Cwrite

Dcallback

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'write' or 'push' instead of 'callback' causes errors.

Forgetting to call 'callback' causes the stream to stall.

In a transform stream, the transform method must call callback() to signal that the chunk has been processed.

4fill in blank

hard

Fill both blanks to create a duplex stream that echoes input data.

Node.js

const { Duplex } = require('stream');
const duplex = new Duplex({
  read(size) {
    // No data to push here
  },
  write(chunk, encoding, [1]) {
    this.push(chunk);
    [2]();
  }
});

Drag options to blanks, or click blank then click option'

Acallback

Bwrite

Cend

Dread

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'write' or 'end' instead of 'callback' causes errors.

Not calling the callback causes the stream to hang.

In the write method of a duplex stream, the third argument is the callback function that must be called to signal completion.

5fill in blank

hard

Fill all three blanks to create a transform stream that reverses input strings.

Node.js

const { Transform } = require('stream');
const reverse = new Transform({
  transform(chunk, encoding, [1]) {
    const input = chunk.toString();
    const reversed = input.split('').[2]().join('');
    this.push(reversed);
    [3]();
  }
});

Drag options to blanks, or click blank then click option'

Acallback

Breverse

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'reverse' as a function argument name causes errors.

Forgetting to call callback causes the stream to stall.

The transform method uses the callback function to signal completion. The string is reversed by splitting, reversing, and joining. Both {{BLANK_1}} and {{BLANK_3}} are the callback function.