Type alias for functions in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a type alias named Greet for a function that takes a string and returns a string.

Typescript

type Greet = (name: string) => [1];

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

Aboolean

Bnumber

Cvoid

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'number' or 'void' as the return type instead of 'string'.

Forgetting to specify the return type.

The function type alias should specify the return type after the arrow. Since the function returns a string, the correct return type is 'string'.

2fill in blank

medium

Complete the code to declare a variable sayHello with the type alias Greet.

Typescript

let sayHello: [1];

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

AFunction

BGreet

Cstring

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string' as the type instead of the function type alias.

Using 'Function' which is too general.

To use the type alias for a function, assign the variable the type 'Greet'.

3fill in blank

hard

Fix the error in the function implementation to match the Greet type alias.

Typescript

sayHello = function(name: string): [1] {
  return "Hello, " + name;
};

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

Astring

Bvoid

Cnumber

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'void' or 'number' as the return type causing type errors.

Omitting the return type.

The function must return a string to match the 'Greet' type alias.

4fill in blank

hard

Fill both blanks to define a type alias MathOp for a function taking two numbers and returning a number.

Typescript

type MathOp = (a: [1], b: [2]) => number;

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

Anumber

Bstring

Cboolean

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string' or 'boolean' as parameter types.

Mixing different types for parameters.

Both parameters should be of type 'number' to match the function signature.

5fill in blank

hard

Fill all three blanks to create a variable multiply of type MathOp that multiplies two numbers.

Typescript

const multiply: [1] = (x: [2], y: [3]) => x * y;

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

AMathOp

Bnumber

Cstring

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong types for parameters or variable type.

Forgetting to use the type alias for the variable.

The variable 'multiply' must have type 'MathOp'. The parameters 'x' and 'y' must be numbers.