Why async patterns are critical in Node.js in Node.js - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read a file asynchronously using Node.js built-in module.

Node.js

import { readFile } from 'fs/promises';

async function readData() {
  const data = await readFile('[1]', 'utf8');
  console.log(data);
}

readData();

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

A'./data.txt'

B'data.txt'

C'./data.json'

D'data.json'

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting './' causes file not found errors.

Using synchronous readFileSync instead of async readFile.

The path './data.txt' correctly points to the file in the current directory. Using await with readFile reads the file asynchronously.

2fill in blank

medium

Complete the code to handle an asynchronous operation with a callback in Node.js.

Node.js

import { readFile } from 'fs';

readFile('[1]', 'utf8', (err, data) => {
  if (err) {
    console.error(err);
    return;
  }
  console.log(data);
});

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

A'file.json'

B'./file.txt'

C'./file.json'

D'file.txt'

Attempts:

3 left

💡 Hint

Common Mistakes

Using synchronous readFileSync instead of async readFile.

Incorrect file path causing errors.

The path './file.txt' correctly points to the file in the current directory. The callback handles the asynchronous read operation.

3fill in blank

hard

Fix the error in the async function to properly catch errors using try-catch.

Node.js

import { readFile } from 'fs/promises';

async function loadFile() {
  [1] {
    const content = await readFile('./info.txt', 'utf8');
    console.log(content);
  } catch (error) {
    console.error('Error:', error);
  }
}

loadFile();

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

Afinally

Bcatch

Ctry

Dawait

Attempts:

3 left

💡 Hint

Common Mistakes

Using catch without try causes syntax errors.

Not handling errors leads to unhandled promise rejections.

The try block is needed to wrap the await call so errors can be caught in the catch block.

4fill in blank

hard

Fill both blanks to create a Promise that resolves after a delay and use async/await to wait for it.

Node.js

function delay(ms) {
  return new Promise(([1], reject) => {
    setTimeout(() => [2](), ms);
  });
}

async function run() {
  console.log('Start');
  await delay(1000);
  console.log('End after 1 second');
}

run();

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

Aresolve

Breject

Cresolve()

Dreject()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling reject() instead of resolve() causes the Promise to fail.

Not calling resolve() leaves the Promise pending forever.

The Promise constructor receives resolve and reject functions. Calling resolve() inside setTimeout signals the Promise is done.

5fill in blank

hard

Fill all three blanks to create an async function that fetches JSON data and handles errors.

Node.js

import fetch from 'node-fetch';

async function getData(url) {
  try {
    const response = await fetch([1]);
    if (!response.ok) throw new Error('Network error');
    const data = await response.[2]();
    return [3];
  } catch (err) {
    console.error('Fetch failed:', err);
  }
}

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

Aurl

Bjson

Cdata

Dtext

Attempts:

3 left

💡 Hint

Common Mistakes

Using response.text() instead of response.json() for JSON data.

Not returning the parsed data from the function.

The fetch function takes the URL. The response.json() method parses JSON data. Returning data gives the caller the fetched content.