Default generic types in Typescript - Cheat Sheet & Quick Revision

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What are default generic types in TypeScript?

Default generic types are preset types given to generic parameters so that if no type is provided when using the generic, the default is used automatically.

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How do you specify a default generic type in TypeScript?

You specify a default generic type by using an equals sign after the generic parameter name, like <T = string>.

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Consider this code: <br>

function example<T = number>(value: T): T { return value; }

<br>What happens if you call example() without specifying a type?

The function uses the default generic type number, so TypeScript treats value as a number.

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Why are default generic types useful?

They make generics easier to use by providing a fallback type, so users don’t always have to specify the type explicitly.

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Can you override a default generic type when calling a generic function?

Yes, you can provide a specific type when calling the function, which replaces the default generic type.

What does this syntax mean in TypeScript? function foo() {}

A T is a function returning string

B T must always be string

C T is a variable of type string

D T is a generic type defaulting to string if not specified

The syntax means T is a generic type parameter with a default type of string.

If a generic function has a default type, what happens when you call it without specifying a type?

A It uses the default generic type

B It causes a compile error

C It uses any type

D It uses void type

When no type is specified, the default generic type is used automatically.

How do you override a default generic type when calling a generic function?

A By passing the type as a function argument

B By specifying the type in angle brackets after the function name

C By changing the default type in the function definition

D You cannot override the default type

You override the default by specifying the type explicitly, like foo().

Which of these is a benefit of default generic types?

A They reduce the need to specify types every time

B They make code run faster

C They prevent any type errors

D They force all generics to be strings

Default generic types make generics easier to use by providing a fallback type.

What happens if you specify a generic type when a default is already set?

A TypeScript throws an error

B The default type is used anyway

C The specified type replaces the default

D The function ignores the generic type

The explicitly provided type overrides the default generic type.

Explain what default generic types are and why they are useful in TypeScript.

Think about how generics work and what happens if you don't specify a type.

Describe how to declare a default generic type and how to override it when calling a generic function.

Remember the equals sign in the generic parameter and how to call generic functions.