Parameter properties shorthand in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the parameter properties shorthand in TypeScript?

It is a way to declare and initialize class properties directly in the constructor parameters by adding an access modifier (like <code>public</code>, <code>private</code>, or <code>protected</code>) before the parameter name.

beginner

How does parameter properties shorthand help when writing classes?

It reduces the amount of code by combining property declaration and assignment into one step inside the constructor, making the code shorter and easier to read.

beginner

Rewrite this class using parameter properties shorthand:<br><pre>class Person {
  name: string;
  constructor(name: string) {
    this.name = name;
  }
}</pre>

<pre>class Person {
  constructor(public name: string) {}
}</pre>

intermediate

Which access modifiers can be used with parameter properties shorthand?

You can use public, private, protected, and readonly modifiers to control visibility and mutability of the property.

beginner

True or False: Parameter properties shorthand can only be used with public parameters.

False. Parameter properties shorthand can be used with public, private, protected, and readonly parameters.

What does the parameter properties shorthand do in TypeScript?

A Declares and initializes class properties directly in constructor parameters

B Creates global variables automatically

C Defines functions inside constructor parameters

D Removes the need for constructors

Parameter properties shorthand lets you declare and initialize class properties in one step inside the constructor parameters.

Which of these is a valid use of parameter properties shorthand?

A constructor(private age: number) {}

B constructor(age: number) { this.age = age; }

C constructor(age) { this.age = age; }

D constructor(public age) { age = 10; }

Using an access modifier like private before the parameter name declares and initializes the property automatically.

What happens if you omit the access modifier in a constructor parameter?

A The parameter becomes a class property

B The parameter is just a normal parameter, no property is created

C The code will not compile

D The parameter becomes a global variable

Without an access modifier, the parameter is only a normal parameter and does not create a class property.

Can you use readonly with parameter properties shorthand?

A Only with <code>public</code> modifier

B No, <code>readonly</code> is not allowed

C Only with <code>private</code> modifier

D Yes, to make the property immutable

readonly can be used to make the property immutable after initialization.

Which of these is NOT a benefit of parameter properties shorthand?

A Less code to write

B Combines declaration and assignment

C Automatically creates getter and setter methods

D Improves readability

Parameter properties shorthand does not create getter or setter methods automatically.

Explain how parameter properties shorthand works and why it is useful.

Think about how you normally declare properties and assign them in the constructor.

Write a simple TypeScript class using parameter properties shorthand with at least two properties.

Use public or private before the parameter names in the constructor.