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JavaScript runtime 1.0 features for CloudFront Functions - Amazon CloudFront
Core featuresPrimitive objectsBuilt-in objectsError typesGlobalsBuilt-in modulesRestricted features

JavaScript runtime 1.0 features for CloudFront Functions

The CloudFront Functions JavaScript runtime environment is compliant with ECMAScript (ES) version 5.1 and also supports some features of ES versions 6 through 9. It also provides some nonstandard methods that are not part of the ES specifications.

The following topics list all the supported language features.

Core features

The following core features of ES are supported.

Types

All ES 5.1 types are supported. This includes Boolean values, numbers, strings, objects, arrays, functions, function constructors, and regular expressions.

Operators

All ES 5.1 operators are supported.

The ES 7 exponentiation operator (**) is supported.

Statements
Note

The const and let statements are not supported.

The following ES 5.1 statements are supported:

  • break

  • catch

  • continue

  • do-while

  • else

  • finally

  • for

  • for-in

  • if

  • return

  • switch

  • throw

  • try

  • var

  • while

  • Labeled statements

Literals

ES 6 template literals are supported: multiline strings, expression interpolation, and nesting templates.

Functions

All ES 5.1 function features are supported.

ES 6 arrow functions are supported, and ES 6 rest parameter syntax is supported.

Unicode

Source text and string literals can contain Unicode-encoded characters. Unicode code point escape sequences of six characters (for example, \uXXXX) are also 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 are supported.

Object

The following ES 5.1 methods on objects are supported:

  • create (without properties list)

  • defineProperties

  • defineProperty

  • freeze

  • getOwnPropertyDescriptor

  • getOwnPropertyNames

  • getPrototypeOf

  • hasOwnProperty

  • isExtensible

  • isFrozen

  • prototype.isPrototypeOf

  • isSealed

  • keys

  • preventExtensions

  • prototype.propertyIsEnumerable

  • seal

  • prototype.toString

  • prototype.valueOf

The following ES 6 methods on objects are supported:

  • assign

  • is

  • prototype.setPrototypeOf

The following ES 8 methods on objects are supported:

  • entries

  • values

String

The following ES 5.1 methods on strings are supported:

  • fromCharCode

  • prototype.charAt

  • prototype.concat

  • prototype.indexOf

  • prototype.lastIndexOf

  • prototype.match

  • prototype.replace

  • prototype.search

  • prototype.slice

  • prototype.split

  • prototype.substr

  • prototype.substring

  • prototype.toLowerCase

  • prototype.trim

  • prototype.toUpperCase

The following ES 6 methods on strings are supported:

  • fromCodePoint

  • prototype.codePointAt

  • prototype.endsWith

  • prototype.includes

  • prototype.repeat

  • prototype.startsWith

The following ES 8 methods on strings are supported:

  • prototype.padStart

  • prototype.padEnd

The following ES 9 methods on strings are supported:

  • prototype.trimStart

  • prototype.trimEnd

The following nonstandard methods on strings are supported:

  • prototype.bytesFrom(array | string, encoding)

    Creates a byte string from an array of octets or an encoded string. The string encoding options are hex, base64, and base64url.

  • prototype.fromBytes(start[, end])

    Creates a Unicode string from a byte string where each byte is replaced with the corresponding Unicode code point.

  • prototype.fromUTF8(start[, end])

    Creates a Unicode string from a UTF-8 encoded byte string. If the encoding is incorrect, it returns null.

  • prototype.toBytes(start[, end])

    Creates a byte string from a Unicode string. All characters must be in the [0,255] range. If not, it returns null.

  • prototype.toUTF8(start[, end])

    Creates a UTF-8 encoded byte string from a Unicode string.

Number

All ES 5.1 methods on numbers are supported.

The following ES 6 methods on numbers are supported:

  • isFinite

  • isInteger

  • isNaN

  • isSafeInteger

  • parseFloat

  • parseInt

  • prototype.toExponential

  • prototype.toFixed

  • prototype.toPrecision

  • EPSILON

  • MAX_SAFE_INTEGER

  • MAX_VALUE

  • MIN_SAFE_INTEGER

  • MIN_VALUE

  • NEGATIVE_INFINITY

  • NaN

  • POSITIVE_INFINITY

Built-in objects

The following built-in objects of ES are supported.

Math

All ES 5.1 math methods are supported.

Note

In the CloudFront Functions runtime environment, the Math.random() implementation uses OpenBSD arc4random seeded with the timestamp of when the function runs.

The following ES 6 math methods are supported:

  • acosh

  • asinh

  • atanh

  • cbrt

  • clz32

  • cosh

  • expm1

  • fround

  • hypot

  • imul

  • log10

  • log1p

  • log2

  • sign

  • sinh

  • tanh

  • trunc

  • E

  • LN10

  • LN2

  • LOG10E

  • LOG2E

  • PI

  • SQRT1_2

  • SQRT2

Date

All ES 5.1 Date features are supported.

Note

For security reasons, Date always returns the same value—the function’s start time—during the lifetime of a single function run. For more information, see Restricted features.

Function

The apply, bind, and call methods are supported.

Function constructors are not supported.

Regular expressions

All ES 5.1 regular expression features are supported. The regular expression language is Perl compatible. ES 9 named capture groups are supported.

JSON

All ES 5.1 JSON features are supported, including parse and stringify.

Array

The following ES 5.1 methods on arrays are supported:

  • isArray

  • prototype.concat

  • prototype.every

  • prototype.filter

  • prototype.forEach

  • prototype.indexOf

  • prototype.join

  • prototype.lastIndexOf

  • prototype.map

  • prototype.pop

  • prototype.push

  • prototype.reduce

  • prototype.reduceRight

  • prototype.reverse

  • prototype.shift

  • prototype.slice

  • prototype.some

  • prototype.sort

  • prototype.splice

  • prototype.unshift

The following ES 6 methods on arrays are supported:

  • of

  • prototype.copyWithin

  • prototype.fill

  • prototype.find

  • prototype.findIndex

The following ES 7 methods on arrays are supported:

  • prototype.includes

Typed arrays

The following ES 6 typed arrays are supported:

  • Int8Array

  • Uint8Array

  • Uint8ClampedArray

  • Int16Array

  • Uint16Array

  • Int32Array

  • Uint32Array

  • Float32Array

  • Float64Array

  • prototype.copyWithin

  • prototype.fill

  • prototype.join

  • prototype.set

  • prototype.slice

  • prototype.subarray

  • prototype.toString

ArrayBuffer

The following methods on ArrayBuffer are supported:

  • prototype.isView

  • prototype.slice

Promise

The following methods on promises are supported:

  • reject

  • resolve

  • prototype.catch

  • prototype.finally

  • prototype.then

Crypto

The cryptographic module provides standard hashing and hash-based message authentication code (HMAC) helpers. You can load the module using require('crypto'). The module exposes the following methods that behave exactly as their Node.js counterparts:

  • createHash(algorithm)

  • hash.update(data)

  • hash.digest([encoding])

  • createHmac(algorithm, secret key)

  • hmac.update(data)

  • hmac.digest([encoding])

For more information, see Crypto (hash and HMAC) in the built-in modules section.

Console

This is a helper object for debugging. It only supports the log() method, to record log messages.

Note

CloudFront Functions doesn't support comma syntax, such as console.log('a', 'b'). Instead, use the console.log('a' + ' ' + 'b') format.

Error types

The following error objects are supported:

  • Error

  • EvalError

  • InternalError

  • MemoryError

  • RangeError

  • ReferenceError

  • SyntaxError

  • TypeError

  • URIError

Globals

The globalThis object is supported.

The following ES 5.1 global functions are supported:

  • decodeURI

  • decodeURIComponent

  • encodeURI

  • encodeURIComponent

  • isFinite

  • isNaN

  • parseFloat

  • parseInt

The following global constants are supported:

  • NaN

  • Infinity