Static members with types in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a static member in a TypeScript class?

A static member is a property or method that belongs to the class itself, not to any instance of the class. You can access it using the class name without creating an object.

beginner

How do you declare a static property with a type in TypeScript?

Use the static keyword before the property name and specify its type like this: static count: number;

intermediate

Can static methods access instance properties directly? Why or why not?

No, static methods cannot access instance properties directly because they belong to the class, not to any specific object. Instance properties need an object to exist.

beginner

How do you call a static method in TypeScript?

You call it using the class name followed by the method name, like <code>ClassName.methodName()</code>, without creating an instance.

intermediate

What is the benefit of typing static members in TypeScript?

Typing static members helps catch errors early by ensuring the correct data types are used. It also improves code readability and helps tools provide better suggestions.

How do you access a static property named total in a class called Counter?

A Counter.total

B this.total

C new Counter().total

D total

Static properties are accessed using the class name, so Counter.total is correct.

Which keyword is used to declare a static member in TypeScript?

A static

B const

C let

D readonly

The static keyword declares static members in a class.

Can a static method access instance properties directly?

A Yes, always

B Only if the method is marked as private

C Only if the instance is passed as a parameter

D No, because static methods belong to the class, not instances

Static methods cannot access instance properties directly because they do not belong to any object instance.

What happens if you try to access a static property through an instance?

A It deletes the static property

B It works normally

C It will cause a TypeScript error

D It creates a new property on the instance

Accessing static properties through instances is not allowed and TypeScript will show an error.

Why is it useful to type static members in TypeScript?

A To allow static members to change types dynamically

B To catch type errors early and improve code clarity

C To make the code run faster

D To prevent the class from being instantiated

Typing static members helps catch mistakes early and makes the code easier to understand.

Explain what static members are in TypeScript and how you declare them with types.

Think about how static members belong to the class, not instances.

Describe how to access static members and why static methods cannot access instance properties directly.

Remember static means 'belonging to the class itself'.