# Constants

Shared constants for customizations.

## Installation

```yarn
yarn add @commercetools-frontend/constants
```

```npm
npm --save install @commercetools-frontend/constants 
```

## Useful variables

- `GRAPHQL_TARGETS`: Contains the supported [GraphQL targets](https://docs.commercetools.com/merchant-center-customizations/concepts/merchant-center-api.md#graphql) to use in the Apollo Client queries and mutations. For more information, see [Data fetching](https://docs.commercetools.com/merchant-center-customizations/development/data-fetching.md).
- `MC_API_PROXY_TARGETS`: Contains the supported [Proxy targets](https://docs.commercetools.com/merchant-center-customizations/concepts/merchant-center-api.md#proxytarget) to use in the REST API requests. For more information, see [Data fetching](https://docs.commercetools.com/merchant-center-customizations/development/data-fetching.md).
- `DOMAINS`: Contains the supported notification domains. For more information, see [Notifications](https://docs.commercetools.com/merchant-center-customizations/development/notifications.md#notification-system).
- `NOTIFICATION_KINDS_SIDE`: Contains the supported kinds of side notification. For more information, see [Notifications](https://docs.commercetools.com/merchant-center-customizations/development/notifications.md#side-notifications).
- `NOTIFICATION_KINDS_PAGE`: Contains the supported kinds of page notification. For more information, see [Notifications](https://docs.commercetools.com/merchant-center-customizations/development/notifications.md#page-notifications).

## Related pages

- [Section overview page](https://docs.commercetools.com/merchant-center-customizations.md)
- [Previous page: Application components](https://docs.commercetools.com/merchant-center-customizations/tooling-and-configuration/commercetools-frontend-application-components.md)
- [Next page: Cypress](https://docs.commercetools.com/merchant-center-customizations/tooling-and-configuration/commercetools-frontend-cypress.md)