@ava/babel-preset-stage-4 

> [Babel] preset for use with [AVA]

Aspires to bring finished ECMAScript proposals to AVA's test and helper files.

Efficiently applies the minimum of transforms to run the latest JavaScript syntax on Node.js 8, 10 and 12.

Built-ins are not added or extended, so features like Proxies, Array.prototype.includes or String.prototype.padStart will only be available if the Node.js version running the tests supports it. Consult [node.green] for details.

Sometimes a particular feature is mostly implemented in Node.js. In that case transforms are not applied.

Not all proposals can be supported via Babel transforms, see below for details. Babel may require "syntax" plugins in order to parse certain files. These plugins should be applied explicitly since this preset may not include them.

Install

``console
$ npm install --save @ava/babel-preset-stage-4
`

Usage

Add @ava/stage-4 to your [Babel] presets.

$3

For more information on setting options for a preset, refer to the [preset options] documentation.

#### modules

By default this preset transform ES2015 modules to CommonJS. Set to false to disable this behavior. Other values are ignored.

Supported proposals

| Proposal | Supported
| ------------------------------------------------------------------------ | ---------
| [Array.prototype.includes][array-includes] | No
| [Object.values/Object.entries][object-values-entries] | No
| [String padding][string-padding] | No
| [Object.getOwnPropertyDescriptors][object-gopds] | No
| [Trailing commas in function parameter lists and calls][function-commas] | Yes
| [Shared memory and atomics][atomics] | No
| [Lifting template literal restriction][template-literal-lift] | No
| [s (dotAll) flag for regular expressions][dot-all] | Yes
| [RegExp named capture groups][named-groups] | No
| [RegExp Lookbehind Assertions][lookbehind] | No
| [RegExp Unicode Property Escapes][unicode-escapes] | No
| [Promise.prototype.finally][finally] | No
| [Asynchronous Iteration][async-iteration] | Partially†
| [Optional catch binding][optional-catch] | Yes
| [JSON superset][json-superset] | No
| [Symbol.prototype.description][symbol-description] | No
| [Function.prototype.toString revision][function-tostring-revision] | No
| [Object.fromEntries][object-fromentries] | No
| [Well-formed JSON.stringify][well-formed-stringify] | No
| [String.prototype.{trimStart,trimEnd}][string-left-right-trim] | No
| [Array.prototype.{flat,flatMap}][flatmap] | No
| [String.prototype.matchAll][string-matchall] | No
| [import()][dynamic-import] | Yes
| [Promise.allSettled][promise-allsettled] | No

† @babel/plugin-proposal-async-generator-functions relies on Symbol.asyncIterator`, which AVA does not polyfill for you.

[AVA]: https://ava.li
[Babel]: https://babeljs.io
[node.green]: http://node.green
[preset options]: http://babeljs.io/docs/plugins/#pluginpreset-options

[array-includes]: https://github.com/tc39/Array.prototype.includes
[object-values-entries]: https://github.com/tc39/proposal-object-values-entries
[string-padding]: https://github.com/tc39/proposal-string-pad-start-end
[object-gopds]: https://github.com/ljharb/proposal-object-getownpropertydescriptors
[function-commas]: https://github.com/tc39/proposal-trailing-function-commas
[atomics]: https://github.com/tc39/ecmascript_sharedmem
[template-literal-lift]: https://github.com/tc39/proposal-template-literal-revision
[dot-all]: https://github.com/tc39/proposal-regexp-dotall-flag
[named-groups]: https://github.com/tc39/proposal-regexp-named-groups
[lookbehind]: https://github.com/tc39/proposal-regexp-lookbehind
[unicode-escapes]: https://github.com/tc39/proposal-regexp-unicode-property-escapes
[finally]: https://github.com/tc39/proposal-promise-finally
[async-iteration]: https://github.com/tc39/proposal-async-iteration
[optional-catch]: https://github.com/tc39/proposal-optional-catch-binding
[json-superset]: https://github.com/tc39/proposal-json-superset
[symbol-description]: https://github.com/tc39/proposal-Symbol-description
[function-tostring-revision]: https://github.com/tc39/Function-prototype-toString-revision
[object-fromentries]: https://github.com/tc39/proposal-object-from-entries
[well-formed-stringify]: https://github.com/tc39/proposal-well-formed-stringify
[string-left-right-trim]: https://github.com/tc39/proposal-string-left-right-trim
[flatmap]: https://github.com/tc39/proposal-flatMap
[string-matchall]: https://github.com/tc39/String.prototype.matchAll
[dynamic-import]: https://github.com/tc39/proposal-dynamic-import
[promise-allsettled]: https://github.com/tc39/proposal-promise-allSettled