README.adoc

babel-preset-njs

A Babel preset for transforming JavaScript code with modern language features into code compatible with njs (NGINX JavaScript). This preset includes support for all the ECMAScript features up to ES2021 — see Plugins for a complete list.

TIP: Take a look at njs-typescript-starter for a complete starter template for developing njs scripts for NGINX server in TypeScript (including integration tests).

Installation

# using npm:
npm install --save-dev babel-preset-njs
# or using yarn:
yarn add --dev babel-preset-njs

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)

{
  "presets": ["babel-preset-njs"]
}

Via CLI

babel --presets babel-preset-njs script.js

Via Node API

require('@babel/core').transform('code', {
  presets: [require('babel-preset-njs')],
})

Plugins

The following table lists all relevant 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.

Plugin	ECMAScript	State	Notes
member-expression-literals	ES3	✗ not needed
property-literals	ES3	✗ not needed
reserved-words	ES3	✗ not needed
property-mutators	ES5	✗ not needed
arrow-functions	ES2015	✗ not needed
block-scoped-functions	ES2015	✗ not needed
block-scoping	ES2015	✗ not needed	since njs 0.6.0
classes	ES2015	✓ included
computed-properties	ES2015	✗ not needed	since njs 0.3.4
destructuring	ES2015	✓ included
duplicate-keys	ES2015	✗ not needed
for-of	ES2015	✗ not needed
function-name	ES2015	⚠ incompatible	njs bug #360
instanceof	ES2015	✗ not needed
literals	ES2015	✗ not needed
new-target	ES2015	✗ not needed
object-super	ES2015	✓ included
parameters	ES2015	✓ included	Only rest parameters are supported.
shorthand-properties	ES2015	✗ not needed
spread	ES2015	✓ included
sticky-regex	ES2015	✗ not needed	since njs 0.6.0
template-literals	ES2015	✗ not needed
typeof-symbol	ES2015	✗ not needed
unicode-escapes	ES2015	✗ not needed	Supported, but not in identifiers (e.g. variable name).
unicode-regex	ES2015	✓ included
exponentiation-operator	ES2016	✗ not needed
async-to-generator	ES2017	✗ not needed	since njs 0.7.0
async-generator-functions	ES2018	⚠ incompatible	njs doesn’t support generators yet
dotall-regex	ES2018	✓ included
named-capturing-groups-regex	ES2018	✗ not needed
object-rest-spread	ES2018	✓ included
unicode-property-regex	ES2018	✓ included
optional-catch-binding	ES2019	✓ included
json-strings	ES2019	✗ not needed
dynamic-import	ES2020	⚠ incompatible	njs has only limited support of ES modules.
export-namespace-from	ES2020	✓ included
nullish-coalescing-operator	ES2020	✗ not needed
optional-chaining	ES2020	✓ included
logical-assignment-operators	ES2021	✓ included
numeric-separator	ES2021	✗ not needed

Enabled Assumptions

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

• constantSuper (classes)

• noClassCalls (classes)

• setClassMethods (classes)

• superIsCallableConstructor (classes)

• ignoreFunctionLength (parameters)

• iterableIsArray (for-of, spread, destructuring)

• noDocumentAll

• noNewArrows

• setSpreadProperties (object-rest-spread)

References

• njs ECMAScript Compatibility

License

This project is licensed under MIT License.