Generic class syntax in Typescript - Cheat Sheet & Quick Revision

Recall & Review

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What is a generic class in TypeScript?

A generic class is a class that can work with any data type, specified when creating an instance. It uses a placeholder type (like <T>) to allow flexibility.

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How do you declare a generic class in TypeScript?

You add a type parameter in angle brackets after the class name, for example: <code>class Box&lt;T&gt; { ... }</code> where <code>T</code> is the placeholder type.

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What does T represent in a generic class?

T is a type parameter that acts like a variable for a type. It gets replaced by a real type when you create an instance of the class.

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How do you create an instance of a generic class with a specific type?

You specify the type inside angle brackets when creating the object, like <code>let box = new Box&lt;string&gt;();</code> to make <code>T</code> equal to <code>string</code>.

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Why use generic classes instead of regular classes?

Generic classes let you write flexible and reusable code that works with many types without repeating the same class for each type.

How do you declare a generic class named Container with a type parameter?

A class Container {}

B class Container<T> {}

C class Container<T>[] {}

D class Container[] {}

The correct syntax for a generic class uses angle brackets with a type parameter, like class Container<T> {}.

What does the T in class Box<T> represent?

A A function

B A specific type like string

C A variable name

D A placeholder for any type

T is a placeholder type that will be replaced by a real type when the class is used.

How do you create an instance of Box for numbers?

A let box = new Box<number>();

B let box = new Box();

C let box = new Box<string>();

D let box = Box<number>;

You specify the type inside angle brackets when creating the instance: new Box<number>().

Why are generic classes useful?

A They allow code reuse with different types

B They only work with strings

C They make code slower

D They replace functions

Generic classes let you reuse the same code for many types, making your code flexible and easier to maintain.

Which of these is NOT a correct way to declare a generic class?

A class Data<T, U> {}

B class Data<U> {}

C class Data[] {}

D class Data<T> {}

Generic classes require type parameters in angle brackets, not square brackets.

Explain how to declare and use a generic class in TypeScript.

Think about how you tell the class what type it should work with.

Why would you choose a generic class over a normal class?

Consider how you can write one class that fits many needs.