@babel/helper-create-class-features-plugin

What is @babel/helper-create-class-features-plugin?

The @babel/helper-create-class-features-plugin is a helper package used internally by Babel plugins to handle the transformation of class features. It is not intended to be used directly by end users, but rather as a utility for plugin authors to create transformations for class properties, private methods, and other class-related syntax in a consistent way.

What are @babel/helper-create-class-features-plugin's main functionalities?

Class Properties

This feature allows the transformation of class properties so that they can be compiled into a format that is compatible with environments that do not support the latest ECMAScript standards. The code sample shows how a class property is transformed into a constructor assignment with a helper function.

"use strict";

function _defineProperty(obj, key, value) {
  if (key in obj) {
    Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true });
  } else {
    obj[key] = value;
  }
  return obj;
}

class Example {
  constructor() {
    _defineProperty(this, "state", {});
  }
}

Private Methods

This feature enables the transformation of private methods in a class. The code sample illustrates how a private method is transformed using WeakSets and helper functions to ensure that the method remains private and is not accessible outside the class.

"use strict";

function _classPrivateMethodInitSpec(obj, privateSet) {
  // ...implementation details
}

function _classPrivateMethodGet(receiver, privateSet, fn) {
  // ...implementation details
}

class Example {
  constructor() {
    _classPrivateMethodInitSpec(this, _privateMethod);
  }
}

var _privateMethod = new WeakSet();

Other packages similar to @babel/helper-create-class-features-plugin

@babel/plugin-proposal-class-properties

This package is a Babel plugin that transforms static class properties as well as properties declared with the property initializer syntax. It is similar to @babel/helper-create-class-features-plugin in that it handles class properties, but it is a full plugin that can be added to a Babel configuration, whereas the helper package is used internally by such plugins.

@babel/plugin-proposal-private-methods

Similar to @babel/helper-create-class-features-plugin, this Babel plugin transforms private methods and accessors in classes. It provides the functionality to use private syntax in class bodies and is intended for direct use in Babel configurations, unlike the helper package which is used under the hood by this and other plugins.

README

@babel/helper-create-class-features-plugin

Compile class public and private fields, private methods and decorators to ES6

See our website @babel/helper-create-class-features-plugin for more information.

Install

Using npm:

npm install --save @babel/helper-create-class-features-plugin

or using yarn:

yarn add @babel/helper-create-class-features-plugin

Changelog

v7.27.1 (2025-04-30)

:eyeglasses: Spec Compliance

• babel-parser
  • #17254 Allow using of as lexical declaration within for (@JLHwung)
  • #17230 Disallow get/set in TSPropertySignature (@JLHwung)
• babel-parser, babel-types
  • #17193 Stricter TSImportType options parsing (@JLHwung)

:bug: Bug Fix

• babel-plugin-proposal-destructuring-private, babel-plugin-proposal-do-expressions, babel-traverse
  • #17137 fix: do expressions should allow early exit (@kermanx)
• babel-helper-wrap-function, babel-plugin-transform-async-to-generator
  • #17251 Fix: propagate argument evaluation errors through async promise chain (@magic-akari)
• babel-helper-remap-async-to-generator, babel-plugin-transform-async-to-generator
  • #17231 fix apply()/call() annotated as pure (@Lacsw)
• babel-helper-fixtures, babel-parser
  • #17233 Create ChainExpression within TSInstantiationExpression (@JLHwung)
• babel-generator, babel-parser
  • #17226 Fill optional AST properties when both estree and typescript parser plugin are enabled (Part 2) (@JLHwung)
• babel-parser
  • #17224 Fill optional AST properties when both estree and typescript parser plugin are enabled (Part 1) (@JLHwung)
  • #17080 Fix start of TSParameterProperty (@JLHwung)
• babel-compat-data, babel-preset-env
  • #17228 Update firefox bugfix compat data (@JLHwung)
• babel-traverse
  • #17156 fix: Objects and arrays with multiple references should not be evaluated (@liuxingbaoyu)
• babel-generator
  • #17216 Fix: support const type parameter in generator (@JLHwung)

:nail_care: Polish

• babel-plugin-bugfix-v8-spread-parameters-in-optional-chaining, babel-plugin-proposal-decorators, babel-plugin-transform-arrow-functions, babel-plugin-transform-class-properties, babel-plugin-transform-destructuring, babel-plugin-transform-object-rest-spread, babel-plugin-transform-optional-chaining, babel-plugin-transform-parameters, babel-traverse
  • #17221 Reduce generated names size for the 10th-11th (@nicolo-ribaudo)

:house: Internal

• babel-runtime-corejs2, babel-runtime-corejs3, babel-runtime
  • #17263 Remove unused regenerator-runtime dep in @babel/runtime (@nicolo-ribaudo)
• babel-compat-data, babel-preset-env
  • #17256 Tune plugin compat data (@JLHwung)
• babel-compat-data, babel-standalone
  • #17236 migrate babel-compat-data build script to mjs (@JLHwung)
• Other
  • #17232 Bump typescript-eslint to 8.29.1 (@JLHwung)
  • #17219 test: add basic typescript-eslint integration tests (@JLHwung)
  • #17205 Inline regenerator in the relevant packages (@nicolo-ribaudo)
• babel-register
  • #16844 Migrate @babel/register to cts (@liuxingbaoyu)
• babel-cli, babel-compat-data, babel-core, babel-generator, babel-helper-compilation-targets, babel-helper-fixtures, babel-helper-module-imports, babel-helper-module-transforms, babel-helper-plugin-test-runner, babel-helper-transform-fixture-test-runner, babel-helpers, babel-node, babel-parser, babel-plugin-transform-modules-amd, babel-plugin-transform-modules-commonjs, babel-plugin-transform-modules-systemjs, babel-plugin-transform-modules-umd, babel-plugin-transform-react-display-name, babel-plugin-transform-regenerator, babel-plugin-transform-runtime, babel-plugin-transform-typeof-symbol, babel-plugin-transform-typescript, babel-preset-env, babel-register, babel-standalone, babel-types
  • #17207 Enforce node protocol import (@JLHwung)
• babel-plugin-transform-regenerator
  • #17205 Inline regenerator in the relevant packages (@nicolo-ribaudo)
  • #17205 Inline regenerator in the relevant packages (@nicolo-ribaudo)
• babel-helpers, babel-plugin-transform-async-generator-functions, babel-plugin-transform-regenerator, babel-preset-env, babel-runtime-corejs3
  • #17205 Inline regenerator in the relevant packages (@nicolo-ribaudo)
• babel-helpers, babel-plugin-transform-regenerator
  • #17205 Inline regenerator in the relevant packages (@nicolo-ribaudo)
  • #17205 Inline regenerator in the relevant packages (@nicolo-ribaudo)
• babel-helpers
  • #17205 Inline regenerator in the relevant packages (@nicolo-ribaudo)

:microscope: Output optimization

• babel-helpers, babel-plugin-transform-modules-commonjs, babel-runtime-corejs3
  • #16538 Reduce interopRequireWildcard size (@liuxingbaoyu)
• babel-helpers, babel-plugin-transform-async-generator-functions, babel-plugin-transform-regenerator, babel-preset-env, babel-runtime-corejs3
  • #17213 Reduce regeneratorRuntime size (@liuxingbaoyu)