Can you elaborate on the significance of <abc<xyz>> appearing after a function name in TypeScript?

Learning TypeScript has brought me to new discoveries. While exploring a random project online today, I stumbled upon this intriguing piece of code in a TypeScript file:

import { Route, useRoute } from "@react-navigation/native"
import { NewAppointmentConfirmationScreenProps } from "@app/screens/new-appointment-confirmation/types"

export const useNewAppointmentConfirmationScreenRoute = () =>
  useRoute<Route<"NewAppointmentConfirmationScreen", NewAppointmentConfirmationScreenProps>>()

This function is unfamiliar to me! Can someone explain what this line means:

useRoute<Route<"NewAppointmentConfirmationScreen", NewAppointmentConfirmationScreenProps>>()

I understand that a component looks like <abc/>, but why is there a function name followed by angle brackets (less-than/greater-than signs)?

typescript

Answer №1

It's known as generics

Here is more detailed information on generics.

In essence, generics help us implement strong types in classes using a different syntax.

There's also a helpful video on generics.

Historically, generics have origins in strongly-typed languages like Java and C#.

For instance, when creating an ArrayList in Java, we need to specify the data type within angle brackets similar to your example.

https://i.sstatic.net/a8C8K.png

See the syntax here.

Do you notice the syntax?

ArrayList<String>

If I'm correct, generics are primarily used for defining function parameter types.

**Edit: Just came across this on a .NET 5 page recently.

Check out this link and experiment with the runtime online.

https://i.sstatic.net/v6Ugk.png

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