Why typed functions matter in Typescript - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function that adds two numbers and returns a number.

Typescript

function add(a: number, b: number): [1] {
  return a + b;
}

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

Aboolean

Bstring

Cnumber

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string' or 'void' as return type causes errors.

The function returns a number because it adds two numbers.

2fill in blank

medium

Complete the code to declare a function that takes a string and returns its length as a number.

Typescript

function getLength(text: string): [1] {
  return text.length;
}

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

Astring

Bvoid

Cboolean

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 'string' or 'void' causes type errors.

The length property of a string is a number.

3fill in blank

hard

Fix the error in the function by specifying the correct return type.

Typescript

function isEven(num: number): [1] {
  return num % 2 === 0;
}

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

Aboolean

Bstring

Cnumber

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'number' or 'string' as return type causes errors.

The function returns true or false, so the return type is boolean.

4fill in blank

hard

Fill both blanks to declare a function that takes an array of numbers and returns the sum as a number.

Typescript

function sumArray(arr: [1]): [2] {
  return arr.reduce((acc, val) => acc + val, 0);
}

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

Anumber[]

Bstring[]

Cnumber

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string[]' or 'boolean' for the array or return type causes errors.

The function takes an array of numbers (number[]) and returns a number which is the sum.

5fill in blank

hard

Fill all three blanks to declare a function that takes a string and a number, and returns a string repeated that many times.

Typescript

function repeatText(text: [1], times: [2]): [3] {
  return text.repeat(times);
}

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

Astring

Bnumber

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up parameter types or return type causes errors.

The function takes a string and a number, and returns a string repeated multiple times.