---
title: "ExactlyOne | JavaScript maps SDK"
description: "Documentation for MapTiler SDK"
---

> For AI agents: a documentation index is available at [/llms.txt](https://docs.maptiler.com/llms.txt). Markdown versions of all pages are available by appending .md to any URL.

# Type Alias ExactlyOne<T, Keys>

ExactlyOne: {  
    \[K in [Keys](#keys)\]: [Required](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.Required/)<[Pick](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.Pick/)<[T](#t), K\>\> & { \[P in [Exclude](https://docs.maptiler.com/sdk-js/api-reference/types/Externals.Exclude/)<[Keys](#keys), K\>\]?: never }  
}\[[Keys](#keys)\]

#### Type Parameters

-   T
-   Keys extends keyof [T](#t) = keyof [T](#t)