= babel-preset-njs
:npm-name: babel-preset-njs
:gh-name: jirutka/{npm-name}
:gh-branch: master
:ci-workflow: npmjs
:babel-doc-uri: https://babeljs.io/docs/en
:object-rest-spread-mdn-uri: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax#Spread_in_object_literals
:array-spread-mdn-uri: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax#Spread_in_array_literals
:array-destructuring-mdn-uri: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment#Array_destructuring

ifdef::env-github[]
image:https://img.shields.io/npm/v/{npm-name}.svg[npm Version, link="https://www.npmjs.org/package/{npm-name}"]
image:https://github.com/{gh-name}/workflows/{ci-workflow}/badge.svg[CI State, link=https://github.com/{gh-name}/actions?query=workflow%3A%22{ci-workflow}%22]
endif::env-github[]

A https://babeljs.io[Babel] https://babeljs.io/docs/en/presets[preset] for transforming JavaScript code with modern language features into code compatible with https://github.com/nginx/njs[njs] (NGINX JavaScript).
This preset includes support for all the ECMAScript features up to ES2021 -- see <> for a complete list.

TIP: Take a look at https://github.com/jirutka/njs-typescript-starter[njs-typescript-starter] for a complete starter template for developing njs scripts for https://nginx.org[NGINX] server in https://www.typescriptlang.org[TypeScript] (including integration tests).

== Installation

[source, sh, subs="+attributes"]
----

using npm:

npm install --save-dev {npm-name}

or using yarn:

yarn add --dev {npm-name}
----

=== Compatibility Matrix

|===
| preset-njs | njs | Babel

| 0.1.0 – 0.2.1 | ≥ 0.5.0 | 7
| 0.7.0 | ≥ 0.7.0 | 7
|===

== Usage

=== With a Configuration File (Recommended)

[source, json, subs="+attributes"]
----
{
"presets": ["{npm-name}"]
}
----

=== Via CLI

[source, sh, subs="+attributes"]
babel --presets {npm-name} script.js

=== Via Node API

[source, js, subs="+attributes"]
----
require('@babel/core').transform('code', {
presets: [require('{npm-name}')],
})
----

== Plugins
:babel-plugin-uri: https://babeljs.io/docs/en/babel-plugin
:included: ✓{nbsp}included
:not-needed: ✗{nbsp}not{nbsp}needed
:incompatible: ⚠{nbsp}incompatible

ifdef::npm-readme[]
The list of included Babel plugins is available https://github.com/{gh-name}/blob/{gh-branch}/README.adoc#plugins[here].

endif::npm-readme[]
ifndef::npm-readme[]
The following table lists all relevant https://babeljs.io/docs/en/plugins#transform-plugins[Babel transform plugins] for ECMAScript features up to ES2021.

The State column is one of:

* {included} -- The plugin is included in this preset, i.e. njs doesn’t support this feature (or part of it) yet.
* {not-needed} -- The plugin is not needed, i.e. njs already supports this feature.
* {incompatible} -- The plugin is not compatible with njs, i.e. requires features that njs doesn’t support yet.

| {babel-plugin-uri}-transform-member-expression-literals[member-expression-literals]
| ES3
| {not-needed}
|

| {babel-plugin-uri}-transform-property-literals[property-literals]
| ES3
| {not-needed}
|

| {babel-plugin-uri}-transform-reserved-words[reserved-words]
| ES3
| {not-needed}
|

| {babel-plugin-uri}-transform-property-mutators[property-mutators]
| ES5
| {not-needed}
|

| {babel-plugin-uri}-transform-arrow-functions[arrow-functions]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-block-scoped-functions[block-scoped-functions]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-block-scoping[block-scoping]
| ES2015
| {not-needed}
| since njs 0.6.0

| {babel-plugin-uri}-transform-classes[classes]
| ES2015
| {included}
|

| {babel-plugin-uri}-transform-computed-properties[computed-properties]
| ES2015
| {not-needed}
| since njs 0.3.4

| {babel-plugin-uri}-transform-destructuring[destructuring]
| ES2015
| {included}
|

| {babel-plugin-uri}-transform-duplicate-keys[duplicate-keys]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-for-of[for-of]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-function-name[function-name]
| ES2015
| {incompatible}
| https://github.com/nginx/njs/issues/360[njs bug #360]

| {babel-plugin-uri}-transform-instanceof[instanceof]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-literals[literals]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-new-target[new-target]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-object-super[object-super]
| ES2015
| {included}
|

| {babel-plugin-uri}-transform-parameters[parameters]
| ES2015
| {included}
| Only rest parameters are supported.

| {babel-plugin-uri}-transform-shorthand-properties[shorthand-properties]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-spread[spread]
| ES2015
| {included}
|

| {babel-plugin-uri}-transform-sticky-regex[sticky-regex]
| ES2015
| {not-needed}
| since njs 0.6.0

| {babel-plugin-uri}-transform-template-literals[template-literals]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-typeof-symbol[typeof-symbol]
| ES2015
| {not-needed}
|

| {babel-plugin-uri}-transform-unicode-escapes[unicode-escapes]
| ES2015
| {not-needed}
| Supported, but not in identifiers (e.g. variable name).

| {babel-plugin-uri}-transform-unicode-regex[unicode-regex]
| ES2015
| {included}
|

| {babel-plugin-uri}-transform-exponentiation-operator[exponentiation-operator]
| ES2016
| {not-needed}
|

| {babel-plugin-uri}-transform-async-to-generator[async-to-generator]
| ES2017
| {not-needed}
| since njs 0.7.0

| {babel-plugin-uri}-proposal-async-generator-functions[async-generator-functions]
| ES2018
| {incompatible}
| njs doesn’t support generators yet

| {babel-plugin-uri}-transform-dotall-regex[dotall-regex]
| ES2018
| {included}
|

| {babel-plugin-uri}-transform-named-capturing-groups-regex[named-capturing-groups-regex]
| ES2018
| {not-needed}
|

| {babel-plugin-uri}-proposal-object-rest-spread[object-rest-spread]
| ES2018
| {included}
|

| {babel-plugin-uri}-proposal-unicode-property-regex[unicode-property-regex]
| ES2018
| {included}
|

| {babel-plugin-uri}-proposal-optional-catch-binding[optional-catch-binding]
| ES2019
| {included}
|

| {babel-plugin-uri}-proposal-json-strings[json-strings]
| ES2019
| {not-needed}
|

| {babel-plugin-uri}-proposal-dynamic-import[dynamic-import]
| ES2020
| {incompatible}
| njs has only limited support of ES modules.

| {babel-plugin-uri}-proposal-export-namespace-from[export-namespace-from]
| ES2020
| {included}
|

| {babel-plugin-uri}-proposal-nullish-coalescing-operator[nullish-coalescing-operator]
| ES2020
| {not-needed}
|

| {babel-plugin-uri}-proposal-optional-chaining[optional-chaining]
| ES2020
| {included}
|

| {babel-plugin-uri}-proposal-logical-assignment-operators[logical-assignment-operators]
| ES2021
| {included}
|

| {babel-plugin-uri}-proposal-numeric-separator[numeric-separator]
| ES2021
| {not-needed}
|
|===

== Enabled Assumptions

The following assumptions are enabled for better performance and match with the behaviour of the TypeScript transpiler.

* {babel-doc-uri}/assumptions#constantsuper[constantSuper] ({babel-plugin-uri}-transform-classes#loose[classes])
* {babel-doc-uri}/assumptions#noclasscalls[noClassCalls] ({babel-plugin-uri}-transform-classes#loose[classes])
* {babel-doc-uri}/assumptions#setclassmethods[setClassMethods] ({babel-plugin-uri}-transform-classes#loose[classes])
* {babel-doc-uri}/assumptions#superiscallableconstructor[superIsCallableConstructor] ({babel-plugin-uri}-transform-classes#loose[classes])
* {babel-doc-uri}/assumptions#ignorefunctionlength[ignoreFunctionLength] ({babel-plugin-uri}-transform-parameters#loose[parameters])
* {babel-doc-uri}/assumptions#iterableisarray[iterableIsArray] ({babel-plugin-uri}-transform-for-of#assumearray[for-of], {babel-plugin-uri}-transform-spread#loose[spread], {babel-plugin-uri}-transform-destructuring#loose[destructuring])
* {babel-doc-uri}/assumptions#nodocumentall[noDocumentAll]
* {babel-doc-uri}/assumptions#nonewarrows[noNewArrows]
* {babel-doc-uri}/assumptions#setspreadproperties[setSpreadProperties] ({babel-plugin-uri}-proposal-object-rest-spread#loose[object-rest-spread])

endif::npm-readme[]

== References

* http://nginx.org/en/docs/njs/compatibility.html[njs ECMAScript Compatibility]

== License

This project is licensed under http://opensource.org/licenses/MIT/[MIT License].