Generic arrow functions in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a generic arrow function that returns the input value.

Typescript

const identity = <T>([1]: T): T => [1];

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Ainput

Barg

Citem

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the parameter and return value.

Forgetting to use the generic type .

The generic arrow function takes a parameter named value of type T and returns it.

2fill in blank

medium

Complete the code to declare a generic arrow function that returns the length of an array.

Typescript

const getLength = <T>(arr: T[]): number => arr[1];

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A.size

B.length()

C.length

D.count

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses after length like a function.

Using incorrect property names like size or count.

Arrays in TypeScript have a length property (without parentheses) that returns the number of elements.

3fill in blank

hard

Fix the error in the generic arrow function that swaps two elements in a tuple.

Typescript

const swap = <T, U>(pair: [T, U]): [U, T] => [pair[1]1, pair[0]];

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A[

B{

C(

D.

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot notation before the index like pair.1 which is invalid.

Using parentheses or braces instead of square brackets.

To access tuple elements, use bracket notation with index inside square brackets, like pair[1]. The dot before 1 is incorrect.

4fill in blank

hard

Complete the code to create a generic arrow function that returns the first element of an array.

Typescript

const firstElement = <T>(arr: T]): T | undefined => arr[[1];

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A[

B0

C1

D]

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of square brackets.

Using index 1 instead of 0.

5fill in blank

hard

Fill all three blanks to create a generic arrow function that filters an array by a condition function.

Typescript

const filterArray = <T>(arr: T[], condition: (item: T) => boolean): T[] => arr.filter([1] => [2]([3]));

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Aitem

Ccondition(item)

Dcondition

Attempts:

3 left

💡 Hint

Common Mistakes

Using different parameter names inside and outside the arrow function.

Not calling the condition function properly.

The filter method takes a function with a parameter (here item) and returns true or false by calling condition(item).