Why promises are used in Javascript - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new Promise.

Javascript

const myPromise = new [1]((resolve, reject) => {
  resolve('Done');
});

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

APromise

BFunction

CObject

DArray

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'promise' instead of 'Promise'.

Using 'Function' instead of 'Promise'.

Promises in JavaScript are created using the Promise constructor.

2fill in blank

medium

Complete the code to handle a resolved Promise.

Javascript

myPromise.[1](result => {
  console.log(result);
});

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

Acatch

Bthen

Cfinally

Dresolve

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'catch' to handle success.

Using 'resolve' as a method.

The then method is used to handle the result when a Promise is resolved.

3fill in blank

hard

Fix the error in the code to handle Promise rejection.

Javascript

myPromise.then(result => {
  console.log(result);
}).[1](error => {
  console.error(error);
});

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

Afinally

Bthen

Ccatch

Dresolve

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'then' to catch errors.

Using 'finally' to catch errors.

The catch method is used to handle errors when a Promise is rejected.

4fill in blank

hard

Fill both blanks to create a Promise that rejects on error.

Javascript

const errorPromise = new Promise(([1], [2]) => {
  [1]('Success');
  [2]('Error occurred');
});

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

Aresolve

Breject

Cresult

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping resolve and reject.

Using variable names instead of function names.

The first parameter is resolve to handle success, the second is reject to handle errors.

5fill in blank

hard

Fill all three blanks to create a Promise and handle both success and failure.

Javascript

const promise = new Promise(([1], [2]) => {
  if(true) {
    [1]('Done');
  } else {
    [2]('Failed');
  }
});
promise.[3](message => console.log(message)).catch(error => console.error(error));

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

Aresolve

Breject

Cthen

Dfinally

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'finally' instead of 'then'.

Mixing up resolve and reject.

Use resolve and reject in the Promise constructor, and then to handle success.