Registry / babel-plugin-transform-proto-to-assign

babel-plugin-transform-proto-to-assign

library6.26.0jsnpmunverified

This Babel plugin transforms assignments to __proto__ into a shallow property copy, enabling prototype-like inheritance in environments that do not support __proto__ or Object.setPrototypeOf. The latest stable version is 6.26.0 (2017-01-30), part of Babel 6.x. It is maintained as part of the Babel monorepo but is considered legacy; Babel 7+ discourages use of this plugin and instead recommends using Object.setPrototypeOf or Object.create for performance reasons. The plugin does a shallow clone of all enumerable own properties from the target prototype. It works only with assignments like `obj.__proto__ = proto`, not `Object.setPrototypeOf`. It modifies Object.prototype, which can cause side effects. It is a single-purpose transform, not part of any preset-env. Alternative: use `@babel/plugin-transform-proto-to-assign` for Babel 7. The plugin is deprecated in favor of modern Object.setPrototypeOf.

npm install babel-plugin-transform-proto-to-assign

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · BABEL-PLUGIN-TRANS

babel-plugin-transform-proto-to-assign

javascriptv6.26.0

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

default (plugin)

✓ module.exports = require('babel-plugin-transform-proto-to-assign');

✗ import p from 'babel-plugin-transform-proto-to-assign';

This plugin is designed for Babel 6's CommonJS module system. In Babel 6, plugins are loaded via require; ES import syntax may not work directly. For Babel 7, use @babel/plugin-transform-proto-to-assign.

babel-core transform with plugin

✓ require('babel-core').transform(code, { plugins: ['transform-proto-to-assign'] });

✗ require('babel-core').transform(code, { plugins: [require('babel-plugin-transform-proto-to-assign')] }); // may work but string name is preferred

In Babel 6, plugins can be specified by package name string. Passing the plugin object directly also works but string is standard.

.babelrc configuration

✓ { "plugins": ["transform-proto-to-assign"] }

✗ { "plugins": ["babel-plugin-transform-proto-to-assign"] } // also valid, but shorter name without prefix is typical

Babel automatically resolves the 'babel-plugin-' prefix, so either 'transform-proto-to-assign' or 'babel-plugin-transform-proto-to-assign' works.

Shows installation, configuration, source code with __proto__ assignment, and compilation output.

// Step 1: Install the plugin // npm install --save-dev babel-plugin-transform-proto-to-assign // Step 2: Create .babelrc with the plugin // { // "plugins": ["transform-proto-to-assign"] // } // Step 3: Write source with __proto__ assignment var foo = { a: 1 }; var bar = { b: 2 }; bar.__proto__ = foo; // Step 4: Compile with Babel // npx babel script.js --out-file compiled.js // compiled.js output (simplified): // var _defaults = ...; // _defaults(bar, foo); // Note: Does not support dynamic prototype chain; only shallow copy of properties at assignment time.

Debug

Known issues

deprecatedThis plugin is part of Babel 6 and has no active development. For Babel 7+, use '@babel/plugin-transform-proto-to-assign' instead.

fix

Upgrade to Babel 7+ and install @babel/plugin-transform-proto-to-assign.

affects: >=6.0.0

gotchaThe transform does a shallow copy of properties at the moment of assignment, not a live prototype chain. Changing the prototype later does not affect already-assigned properties.

fix

Use Object.setPrototypeOf or Object.create for proper prototype chain if needed.

affects: >=0.0.0

gotchaModifying Object.prototype can cause performance issues and side effects in other code. Avoid if possible.

fix

Use explicit property assignment or Object.assign instead of __proto__ manipulation.

affects: >=0.0.0

breakingOnly transforms assignments like `obj.__proto__ = value`. Does not handle Object.setPrototypeOf or Reflect.setPrototypeOf.

fix

Add a separate plugin or polyfill if supporting Object.setPrototypeOf is required.

affects: >=0.0.0

Errors

Common errors & fixes

Cannot find module 'babel-plugin-transform-proto-to-assign'

Plugin not installed or not in node_modules.

fix

Run 'npm install --save-dev babel-plugin-transform-proto-to-assign' and ensure node_modules is present.

Error: Plugin .__proto__ is not a function

Attempting to use the plugin with Babel 7 where the package name has changed.

fix

Use '@babel/plugin-transform-proto-to-assign' instead, or downgrade to Babel 6.

TypeError: Cannot set property __proto__ of undefined

Assigning to __proto__ on a non-object value (null/undefined).

fix

Ensure the left-hand side of __proto__ assignment is an object.

Upgrade

Version history

6.26.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/babel/babel ↗

packagehttps://www.npmjs.com/package/babel-plugin-transform-proto-to-assign ↗

homepagehttps://babeljs.io ↗