@babel/plugin-transform-private-methods

What is @babel/plugin-transform-private-methods?

The @babel/plugin-transform-private-methods package is a Babel plugin that allows developers to use private methods and accessors in classes, according to the ECMAScript specifications. This plugin transforms private methods and accessors so that they can be used in environments that do not support them natively.

What are @babel/plugin-transform-private-methods's main functionalities?

Private Method Transformation

This feature allows developers to define private methods in a class, which are not accessible from outside of the class. The plugin will transform these methods so that they are functionally private in environments that do not have native support for private methods.

class MyClass {
  #privateMethod() {
    return 'Hello from private method';
  }

  publicMethod() {
    return this.#privateMethod();
  }
}

const instance = new MyClass();
console.log(instance.publicMethod()); // 'Hello from private method'

Private Accessor Transformation

This feature enables the use of private getters and setters within a class. Similar to private methods, these accessors are transformed by the plugin to maintain their privacy outside of the class.

class MyClass {
  #privateField = 'private value';

  get #privateAccessor() {
    return this.#privateField;
  }

  publicMethod() {
    return this.#privateAccessor;
  }
}

const instance = new MyClass();
console.log(instance.publicMethod()); // 'private value'

Other packages similar to @babel/plugin-transform-private-methods

@babel/plugin-proposal-class-properties

This package allows developers to use class properties, which includes static and instance properties. It can be used in conjunction with @babel/plugin-transform-private-methods to support private class properties, but it does not handle private methods or accessors on its own.

@babel/plugin-proposal-private-property-in-object

This plugin provides support for checking if a private field is in an object. It is complementary to @babel/plugin-transform-private-methods, which handles the transformation of private methods and accessors, but does not include the functionality to check for private field existence.

README

@babel/plugin-transform-private-methods

This plugin transforms private class methods

See our website @babel/plugin-transform-private-methods for more information.

Install

Using npm:

npm install --save-dev @babel/plugin-transform-private-methods

or using yarn:

yarn add @babel/plugin-transform-private-methods --dev

Changelog

v7.25.9 (2024-10-22)

:bug: Bug Fix

• babel-parser, babel-template, babel-types
  • #16905 fix: Keep type annotations in syntacticPlaceholders mode (@liuxingbaoyu)
• babel-helper-compilation-targets, babel-preset-env
  • #16907 fix: support BROWSERSLIST{,_CONFIG} env (@JLHwung)
• Other
  • #16884 Analyze ClassAccessorProperty to prevent the no-undef rule (@victorenator)

:house: Internal

• babel-helper-transform-fixture-test-runner
  • #16914 remove test options flaky (@JLHwung)

:running_woman: Performance

• babel-parser, babel-types
  • #16918 perf: Make VISITOR_KEYS etc. faster to access (@liuxingbaoyu)