# AWS AppSync JavaScript runtime features for resolvers and functions
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The `APPSYNC_JS` runtime environment provides functionality similar to [ECMAScript (ES) version 6.0](https://262.ecma-international.org/6.0/). It supports a subset of its features and provides some additional methods (utilities) that are not part of the ES specifications. The following topics list all the supported language features:
+  [ Supported runtime features ](https://docs.aws.amazon.com/appsync/latest/devguide/supported-features.html) - Learn more about supported core features, primitive objects, built-in objects and functions, etc.
+  [ Built-in utilities ](https://docs.aws.amazon.com/appsync/latest/devguide/built-in-util-js.html) - The util variable contains general utility methods to help you work with data. Unless otherwise specified, all utilities use the UTF-8 character set.
+  [ Built-in modules ](https://docs.aws.amazon.com/appsync/latest/devguide/built-in-modules-js.html) - Learn more about how built-in modules can help write JavaScript resolvers and functions.
+  [ Runtime utilities ](https://docs.aws.amazon.com/appsync/latest/devguide/runtime-utils-js.html) - The runtime library provides utilities to control or modify the runtime properties of your resolvers and functions.
+  [ Time helpers in util.time ](https://docs.aws.amazon.com/appsync/latest/devguide/time-helpers-in-util-time-js.html) - The util.time variable contains datetime methods to help generate timestamps, convert between datetime formats, and parse datetime strings. The syntax for datetime formats is based on [DateTimeFormatter](https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html), which you can reference for further documentation.
+  [ DynamoDB helpers in util.dynamodb ](https://docs.aws.amazon.com/appsync/latest/devguide/dynamodb-helpers-in-util-dynamodb-js.html) - util.dynamodb contains helper methods that make it easier to write and read data to Amazon DynamoDB, such as automatic type mapping and formatting.
+  [ HTTP helpers in util.http ](https://docs.aws.amazon.com/appsync/latest/devguide/http-helpers-in-utils-http-js.html) - The util.http utility provides helper methods that you can use to manage HTTP request parameters and to add response headers.
+  [ Transformation helpers in util.transform ](https://docs.aws.amazon.com/appsync/latest/devguide/transformation-helpers-in-utils-transform-js.html) - util.transform contains helper methods that make it easier to perform complex operations against data sources.
+  [ String helpers in util.str ](https://docs.aws.amazon.com/appsync/latest/devguide/str-helpers-in-util-str-js.html) - util.str contains methods to help with common String operations.
+  [ Extensions ](https://docs.aws.amazon.com/appsync/latest/devguide/extensions-js.html) - extensions contains a set of methods to make additional actions within your resolvers.
+  [ XML helpers in util.xml ](https://docs.aws.amazon.com/appsync/latest/devguide/xml-helpers-in-util-xml-js.html) - util.xml contains methods to help with XML string conversion.

**Note**  
Currently, this reference only applies to runtime version **1.0.0**.