Generic interface for collections in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a generic interface in TypeScript?

A generic interface is a way to define an interface with a placeholder type that can be specified later. It allows the interface to work with any data type while keeping type safety.

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How do you declare a generic interface for a collection of items in TypeScript?

You declare it using angle brackets with a type parameter, for example: interface Collection<T> { add(item: T): void; get(index: number): T; } where T is the generic type.

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Why use a generic interface for collections instead of a specific type?

Using a generic interface lets you reuse the same code for different types of collections, like numbers, strings, or custom objects, without losing type safety or writing duplicate code.

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Example: What does this interface mean? <br>interface Collection<T> { add(item: T): void; get(index: number): T; }

It means the Collection interface works with any type T. It has an add method to add an item of type T, and a get method to get an item of type T by index.

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How do you create a collection of strings using the generic interface Collection<T>?

You specify the type when using the interface, like <code>let stringCollection: Collection&lt;string&gt;</code>. This means the collection will only hold strings.

What does the T represent in interface Collection<T>?

A A function name

B A specific type like string

C A placeholder for any type

D A variable name

T is a placeholder that stands for any type you want to use when you create a collection.

How do you specify the type when using a generic interface?

A By writing the type inside angle brackets after the interface name

B By writing the type before the interface name

C By using a special keyword 'type'

D You cannot specify the type

You specify the type by putting it inside <> after the interface name, like Collection<number>.

Which of these is a benefit of using generic interfaces for collections?

A Reuse code for different data types safely

B Make code run faster

C Avoid using any types

D Automatically convert types

Generic interfaces let you reuse the same code for many types while keeping type safety.

If you have let numbers: Collection<number>, what type of items can you add?

A Only strings

B Only numbers

C Any type

D Only objects

The collection is set to hold numbers only, so you can add only numbers.

What happens if you try to add a string to Collection<number>?

A The program crashes

B It works fine

C The string is converted to number automatically

D TypeScript shows an error

TypeScript will show a type error because the collection expects numbers only.

Explain what a generic interface for collections is and why it is useful.

Think about how you can write one interface that works for many types.

Describe how you would create and use a generic collection interface to store strings.

Focus on how to tell TypeScript the collection holds strings.