Why generics are needed in Typescript - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

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

Typescript

function identity<T>(value: T): T {
  return value;
}

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

Aitem

Binput

Cvalue

Darg

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name that does not match the return statement.

The generic function uses value as the parameter name to return it directly.

2fill in blank

medium

Complete the code to declare a generic array of type T.

Typescript

let items: Array<[1]> = [];

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AT

Bany

Cnumber

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using a specific type like number or string instead of the generic type.

Using T allows the array to hold elements of the generic type.

3fill in blank

hard

Fix the error in the generic function parameter type.

Typescript

function wrapInArray<T>(value: [1]): T[] {
  return [value];
}

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AArray

BT

Cany

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-generic type like Array or object for the parameter.

The parameter type should be the generic type T to match the function's generic parameter.

4fill in blank

hard

Fill both blanks to create a generic function that returns the first element of an array.

Typescript

function firstElement<[1]>(arr: [2][]): [1] {
  return arr[0];
}

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

AT

BU

Attempts:

3 left

💡 Hint

Common Mistakes

Using different generic type names for the parameter and return type.

The generic type parameter T is used both to declare the generic and to type the array elements.

5fill in blank

hard

Fill all three blanks to create a generic function that maps an array of type T to an array of type U.

Typescript

function mapArray<[1], [2]>(arr: [1][], func: (item: [1]) => [2]): [2][] {
  return arr.map(func);
}

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

AT

BU

CV

DW

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the generic type parameters or using inconsistent names.

The function uses generic types T and U to transform an array of T into an array of U.