Multiple generic parameters in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are multiple generic parameters in TypeScript?

They are placeholders for types that allow a function, class, or interface to work with more than one type, making the code flexible and reusable.

beginner

How do you declare a function with two generic parameters in TypeScript?

Use angle brackets with two type variables separated by a comma, like , before the function parameters.

beginner

Example: What does this function do? function pair(first: T, second: U): [T, U] { return [first, second]; }

It takes two values of any types T and U, and returns a tuple (pair) containing both values in order.

intermediate

Why use multiple generic parameters instead of just one?

Because you might want to work with two or more different types at once, keeping their types separate and flexible.

intermediate

Can generic parameters have constraints when using multiple generics?

Yes, each generic parameter can have its own constraint to limit what types it can accept, improving type safety.

How do you declare a function with two generic types T and U in TypeScript?

A function example<T & U>() {}

B function example<T U>() {}

C function example<T, U>() {}

D function example<T; U>() {}

The correct syntax uses a comma between generic parameters inside angle brackets: .

What does this function return? function combine(a: T, b: U): [T, U] { return [a, b]; }

A An array with elements of types T and U

B A single value of type T

C A single value of type U

D A string combining a and b

It returns a tuple (array) containing the two values with their respective types.

Can each generic parameter have its own constraint in multiple generics?

A Yes, each can have different constraints

B No, constraints apply to all generics together

C Only one generic can have a constraint

D Constraints are not allowed with multiple generics

Each generic parameter can have its own constraint to restrict its type.

Why use multiple generic parameters instead of one?

A To make code slower

B To force all types to be the same

C To avoid using types

D To handle multiple different types separately

Multiple generics allow working with different types independently.

Which of these is a valid generic function with two parameters?

A function f<T; U>(x: T, y: U) {}

B function f<T, U>(x: T, y: U) {}

C function f<T U>(x: T, y: U) {}

D function f<T & U>(x: T, y: U) {}

Only option C uses the correct syntax with a comma separating generic parameters.

Explain how to declare and use a function with multiple generic parameters in TypeScript.

Think about how you can pass two different types and keep them separate.

Describe why multiple generic parameters are useful and how constraints can be applied to them.

Consider real-life situations where you want to keep two things different but related.