# AWS AppSync Event API runtime reference
<a name="runtime-reference-overview"></a>

AWS AppSync lets you respond to specific triggers that occur in the service with code that runs on AWS AppSync's JavaScript runtime (APPSYNC\_JS).

The AWS AppSync JavaScript runtime provides a subset of JavaScript libraries, utilities, and features. For a complete list of features and functionality supported by the `APPSYNC_JS` runtime, see [Runtime features](runtime-features-overview.md).

**Topics**
+ [Event handlers overview](event-handlers-overview.md)
+ [Writing event handlers](writing-event-handlers.md)
+ [Configuring utilities for the `APPSYNC_JS` runtime](configure-utilities.md)
+ [Bundling, TypeScript, and source maps for the `APPSYNC_JS` runtime](additional-utilities.md)