Nullish coalescing with types in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign a default value using nullish coalescing.

Typescript

const name = userInput [1] "Guest";

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

A??

B&&

C||

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using || instead of ??. It treats empty strings or 0 as falsey, which is different.

The ?? operator returns the right side if the left side is null or undefined.

2fill in blank

medium

Complete the code to safely assign a number or default using nullish coalescing.

Typescript

const count: number = inputCount [1] 10;

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

A??

B||

C&&

D!

Attempts:

3 left

💡 Hint

Common Mistakes

Using || causes 0 to be replaced by 10, which is incorrect.

The ?? operator ensures count is assigned inputCount unless it is null or undefined, otherwise 10.

3fill in blank

hard

Fix the error in the code by choosing the correct nullish coalescing operator.

Typescript

const result = value [1] fallback;

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

A|

B||

C&&

D??

Attempts:

3 left

💡 Hint

Common Mistakes

Using || causes unintended fallback for falsey but valid values.

The ?? operator is correct here to handle null or undefined values properly.

4fill in blank

hard

Fill both blanks to create a typed variable with nullish coalescing default.

Typescript

const message: string = inputMessage [1] [2];

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

A??

B"No message"

C""

D||

Attempts:

3 left

💡 Hint

Common Mistakes

Using || instead of ??.

Using empty string as default which may be confusing.

Use ?? to check for null or undefined, and default to the string "No message".

5fill in blank

hard

Fill all three blanks to create a typed variable with nullish coalescing and a fallback number.

Typescript

const total: number = (inputTotal [1] [2]) [3] 100;

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

A??

Bnull

D||

Attempts:

3 left

💡 Hint

Common Mistakes

Using ?? in place of || in the first blank causes no fallback.

Using || in the last blank causes fallback on falsey values.

First, inputTotal || null ensures a value or null, then ?? 100 sets fallback if null or undefined.