# Supported runtime features
The sections below describe the supported feature set of the APPSYNC\$1JS runtime.
## Core features
The following core features are supported.
------
#### [ Types ]
The following types are supported:
+ numbers
+ strings
+ booleans
+ objects
+ arrays
+ functions
------
#### [ Operators ]
Operators are supported, including:
+ standard math operators (`+`, `-`, `/`, `%`, `*`, etc.)
+ nullish coalescing operator (`??`)
+ Optional chaining (`?.`)
+ bitwise operators
+ `void` and `typeof` operators
+ spread operators (`...`)
The following operators are not supported:
+ unary operators (`++`, `--`, and `~`)
+ `in` operator
**Note**
Use the `Object.hasOwn` operator to check if the specified property is in the specified object.
------
#### [ Statements ]
The following statements are supported:
+ `const`
+ `let`
+ `var`
+ `break`
+ `else`
+ `for-in`
+ `for-of`
+ `if`
+ `return`
+ `switch`
+ spread syntax
The following are not supported:
+ `catch`
+ `continue`
+ `do-while`
+ `finally`
+ `for(initialization; condition; afterthought)`
**Note**
The exceptions are `for-in` and `for-of` expressions, which are supported.
+ `throw`
+ `try`
+ `while`
+ labeled statements
------
#### [ Literals ]
The following ES 6 [template literals](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals) are supported:
+ Multi-line strings
+ Expression interpolation
+ Nesting templates
------
#### [ Functions ]
The following function syntax is supported:
+ Function declarations are supported.
+ ES 6 arrow functions are supported.
+ ES 6 rest parameter syntax is supported.
------
#### [ Strict mode ]
Functions operate in strict mode by default, so you don’t need to add a `use_strict` statement in your function code. This cannot be changed.
------
## Primitive objects
The following primitive objects of ES and their functions are supported.
------
#### [ Object ]
The following objects are supported:
+ `Object.assign()`
+ `Object.entries()`
+ `Object.hasOwn()`
+ `Object.keys()`
+ `Object.values()`
+ `delete`
------
#### [ String ]
The following strings are supported:
+ `String.prototype.length()`
+ `String.prototype.charAt()`
+ `String.prototype.concat()`
+ `String.prototype.endsWith()`
+ `String.prototype.indexOf()`
+ `String.prototype.lastIndexOf()`
+ `String.raw()`
+ `String.prototype.replace()`
**Note**
Regular expressions are not supported.
However, Java-styled regular expression constructs are supported in the provided parameter. For more information see [Pattern](https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html).
+ `String.prototype.replaceAll()`
**Note**
Regular expressions are not supported.
However, Java-styled regular expression constructs are supported in the provided parameter. For more information see [Pattern](https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html).
+ `String.prototype.slice()`
+ `String.prototype.split()`
+ `String.prototype.startsWith()`
+ `String.prototype.toLowerCase()`
+ `String.prototype.toUpperCase()`
+ `String.prototype.trim()`
+ `String.prototype.trimEnd()`
+ `String.prototype.trimStart()`
------
#### [ Number ]
The following numbers are supported:
+ `Number.isFinite`
+ `Number.isNaN`
------
## Built-in objects and functions
The following functions and objects are supported.
------
#### [ Math ]
The following math functions are supported:
+ `Math.random()`
+ `Math.min()`
+ `Math.max()`
+ `Math.round()`
+ `Math.floor()`
+ `Math.ceil()`
------
#### [ Array ]
The following array methods are supported:
+ `Array.prototype.length`
+ `Array.prototype.concat()`
+ `Array.prototype.fill()`
+ `Array.prototype.flat()`
+ `Array.prototype.indexOf()`
+ `Array.prototype.join()`
+ `Array.prototype.lastIndexOf()`
+ `Array.prototype.pop()`
+ `Array.prototype.push()`
+ `Array.prototype.reverse()`
+ `Array.prototype.shift()`
+ `Array.prototype.slice()`
+ `Array.prototype.sort()`
**Note**
`Array.prototype.sort()` doesn't support arguments.
+ `Array.prototype.splice()`
+ `Array.prototype.unshift()`
+ `Array.prototype.forEach()`
+ `Array.prototype.map()`
+ `Array.prototype.flatMap()`
+ `Array.prototype.filter()`
+ `Array.prototype.reduce()`
+ `Array.prototype.reduceRight()`
+ `Array.prototype.find()`
+ `Array.prototype.some()`
+ `Array.prototype.every()`
+ `Array.prototype.findIndex()`
+ `Array.prototype.findLast()`
+ `Array.prototype.findLastIndex()`
+ `delete`
------
#### [ Console ]
The console object is available for debugging. During live query execution, console log/error statements are sent to Amazon CloudWatch Logs (if logging is enabled). During code evaluation with `evaluateCode`, log statements are returned in the command response.
+ `console.error()`
+ `console.log()`
------
#### [ Function ]
+ The `apply`, `bind`, and `call` methods not are supported.
+ Function constructors are not supported.
+ Passing a function as an argument is not supported.
+ Recursive function calls are not supported.
------
#### [ JSON ]
The following JSON methods are supported:
+ `JSON.parse()`
**Note**
Returns a blank string if the parsed string is not valid JSON.
+ `JSON.stringify()`
------
#### [ Promises ]
Async processes are not supported, and promises are not supported.
**Note**
Network and file system access is not supported within the `APPSYNC_JS` runtime in AWS AppSync. AWS AppSync handles all I/O operations based on the requests made by the AWS AppSync resolver or AWS AppSync function.
------
## Globals
The following global constants are supported:
+ `NaN`
+ `Infinity`
+ `undefined`
+ [https://docs.aws.amazon.com/appsync/latest/devguide/built-in-util-js.html](https://docs.aws.amazon.com/appsync/latest/devguide/built-in-util-js.html)
+ [https://docs.aws.amazon.com/appsync/latest/devguide/extensions-js.html](https://docs.aws.amazon.com/appsync/latest/devguide/extensions-js.html)
+ `runtime`
## Error types
Throwing errors with `throw` is not supported. You can return an error by using `util.error()` function. You can include an error in your GraphQL response by using the `util.appendError` function.
For more information, see [Error utils](https://docs.aws.amazon.com/appsync/latest/devguide/built-in-util-js.html#utility-helpers-in-error-js).