Rest parameters with types in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function with rest parameters typed as numbers.

Typescript

function sum(...numbers: [1]) { return numbers.reduce((a, b) => a + b, 0); }

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

Astring[]

Bnumber[]

Cany

Dboolean[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'any' instead of a specific type.

Forgetting to use array syntax '[]' for rest parameters.

The rest parameter 'numbers' should be typed as an array of numbers, which is 'number[]'.

2fill in blank

medium

Complete the code to type the rest parameter as an array of strings.

Typescript

function greetAll(...greetings: [1]) { greetings.forEach(greet => console.log(greet)); }

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

Astring[]

Bstring

CArray<string>

Dany[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string' instead of 'string[]'.

Using 'any[]' which is less specific.

Rest parameters must be typed as arrays, so 'string[]' is the correct type for an array of strings.

3fill in blank

hard

Fix the error by correctly typing the rest parameter as an array of booleans.

Typescript

function checkFlags(...flags: [1]) { return flags.every(flag => flag === true); }

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

Aany

BArray<boolean>

Cboolean

Dboolean[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'boolean' instead of 'boolean[]'.

Using 'any' which is not specific.

Rest parameters must be typed as arrays, so 'boolean[]' is the correct type for an array of booleans.

4fill in blank

hard

Fill both blanks to declare a function with rest parameters typed as an array of numbers and return their product.

Typescript

function multiplyAll(...[1]: [2]) { return [1].reduce((a, b) => a * b, 1); }

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

Anums

Bnumber[]

Cvalues

Dstring[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string array type instead of number array.

Forgetting to name the rest parameter.

The rest parameter name can be 'nums' and its type should be 'number[]' to represent an array of numbers.

5fill in blank

hard

Fill all three blanks to declare a function with rest parameters typed as strings, filter those longer than 3 characters, and return the filtered array.

Typescript

function filterLongStrings(...[1]: [2]): [2] { return [1].filter(str => str.length > 3); }

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

Awords

Bstring[]

Cnumber[]

Dany[]

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'number[]' or 'any[]' instead of 'string[]'.

Mismatching parameter and return types.

The rest parameter name is 'words', typed as 'string[]'. The function returns the same type 'string[]'.