JavaScript runtime overview - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print 'Hello, world!' to the console.

Javascript

console.[1]('Hello, world!');

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

Alog

Bprint

Cwrite

Decho

Attempts:

3 left

💡 Hint

Common Mistakes

Using console.print or console.write which do not exist in JavaScript.

Trying to use echo which is from other languages.

The console.log method prints messages to the console in JavaScript.

2fill in blank

medium

Complete the code to create a new Promise that resolves with 'Done'.

Javascript

const promise = new Promise((resolve, reject) => { resolve([1]); });

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AError

Bfalse

Cnull

D'Done'

Attempts:

3 left

💡 Hint

Common Mistakes

Passing Error to resolve instead of reject.

Using null or false which are not the intended resolved value.

The Promise resolves with the string 'Done' using resolve('Done').

3fill in blank

hard

Fix the error in the async function to await the promise correctly.

Javascript

async function fetchData() { const result = [1] promise; return result; }

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Apromise.then()

Bresolve

Cawait

Dasync

Attempts:

3 left

💡 Hint

Common Mistakes

Using promise.then() without await inside async function.

Trying to use resolve or async keywords incorrectly.

The await keyword pauses the async function until the promise resolves.

4fill in blank

hard

Fill both blanks to create a setTimeout that logs 'Hi' after 1 second.

Javascript

setTimeout(() => { console.[1]('Hi'); }, [2]);

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

Alog

B1000

C500

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Using console.error instead of console.log.

Using 500 instead of 1000 for delay.

console.log prints the message, and 1000 means 1000 milliseconds (1 second) delay.

5fill in blank

hard

Fill all three blanks to create a Promise that rejects with 'Fail' after 2 seconds.

Javascript

const failPromise = new Promise(([1], [2]) => { setTimeout(() => { [2]('[3]'); }, 2000); });

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

Aresolve

Breject

CFail

DSuccess

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping resolve and reject parameters.

Calling resolve instead of reject to indicate failure.

Using 'Success' instead of 'Fail' as rejection message.

The Promise executor takes resolve and reject. We call reject('Fail') after 2 seconds to reject the promise.