Supported runtime features - Amazon AppSync
Core featuresPrimitive objectsBuilt-in objects and functionsGlobalsError types
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Supported runtime features

The sections below describe the supported feature set of the APPSYNC_JS 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

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 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.

  • String.prototype.replaceAll()

    Note

    Regular expressions are not supported.

  • 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()

JSON

The following JSON methods are supported:

  • JSON.parse()

    Note

    Returns a blank string if the parsed string is not valid JSON.

  • JSON.stringify()

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.

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 Amazon AppSync. Amazon AppSync handles all I/O operations based on the requests made by the Amazon AppSync resolver or Amazon AppSync function.

Globals

The following global constants are supported:

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.