Optional parameters in Typescript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an optional parameter in the function.

Typescript

function greet(name[1] string) {
  console.log(`Hello, ${name}!`);
}

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

A? :

B:?

C?:

D?:=

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the question mark after the colon.

Using spaces between the question mark and colon.

Using an equal sign with the question mark.

In TypeScript, optional parameters are declared by adding a question mark immediately after the parameter name, before the colon.

2fill in blank

medium

Complete the function call to use the optional parameter correctly.

Typescript

function greet(name?: string) {
  if (name) {
    console.log(`Hello, ${name}!`);
  } else {
    console.log('Hello!');
  }
}

greet([1]);

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

A'Alice'

Bundefined

Cnull

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Passing null which is not the same as undefined in TypeScript optional parameters.

Passing 0 which is a number, not a string.

Passing undefined when the goal is to provide a name.

Passing a string like 'Alice' uses the optional parameter. Passing undefined also works but here we want to show usage with a name.

3fill in blank

hard

Fix the error in the function declaration to make the second parameter optional.

Typescript

function multiply(a: number, b[1] number): number {
  return a * b;
}

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

A?:

B?:=

C:?

D? :

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the question mark after the colon.

Using spaces between the question mark and colon.

Using an equal sign with the question mark.

The correct syntax for optional parameters is to place a question mark immediately after the parameter name, before the colon.

4fill in blank

hard

Fill both blanks to create a function with an optional parameter and a default value.

Typescript

function greet(name[1] string[2] = 'Guest') {
  console.log(`Hello, ${name}!`);
}

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

A?:

B=

C ?=

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using ?= which is not valid syntax.

Putting = before the type.

Omitting the question mark for optional parameters.

Optional parameters use ?: and default values use = after the type.

5fill in blank

hard

Fill all three blanks to create a function with two optional parameters and default values.

Typescript

function createUser(name[1] string[2] = 'Anonymous', age[3] number[4] = 18) {
  console.log(`Name: ${name}, Age: ${age}`);
}

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

A?:

B=

C ?=

D:

Attempts:

3 left

💡 Hint

Common Mistakes

Using ?= which is invalid.

Forgetting the question mark for optional parameters.

Placing = before the type.

Optional parameters use ?: and default values use = after the type. Both parameters are optional with defaults.