babel-polyfill-safe

6.6.1 verified Fri May 01 auth: no javascript deprecated

A wrapper around babel-polyfill (v6.6.1) that prevents errors when the polyfill is required multiple times. It checks a global flag to avoid re-applying polyfills, solving the 'only one instance of babel-polyfill is allowed' issue. The package is intended for legacy Babel 6 environments, is no longer actively developed, and users should migrate to @babel/polyfill or direct core-js/regenerator-runtime imports.

Common errors

error Error: only one instance of babel-polyfill is allowed ↓

cause Multiple packages install and import babel-polyfill separately.

fix

Replace all 'babel-polyfill' imports with 'babel-polyfill-safe' in your project and dependencies.

error ReferenceError: regeneratorRuntime is not defined ↓

cause Despite using babel-polyfill-safe, some async/transform require regenerator-runtime which might not be included.

fix

Ensure babel-polyfill (>=6.6.1) is installed; it includes regenerator-runtime.

error Cannot find module 'babel-polyfill' ↓

cause babel-polyfill is a peer dependency but not installed.

fix

Run: npm install babel-polyfill@^6.6.1

Warnings

deprecated babel-polyfill-safe is designed for Babel 6; Babel 7+ uses @babel/polyfill which has its own safety mechanisms. ↓

fix Migrate to @babel/polyfill or directly import core-js/stable and regenerator-runtime/runtime.

gotcha This package only prevents the 'only one instance' error; it does not version-check the polyfill content. If two different versions of babel-polyfill are required, behavior is undefined. ↓

fix Ensure all dependencies use the same version of babel-polyfill; prefer deduplicating via npm/yarn.

gotcha The package sets global._babelPolyfill = true after first require, which may conflict with other polyfill libraries that check the same global flag. ↓

fix Avoid mixing multiple polyfill wrappers; stick to one official method.

Install

npm install babel-polyfill-safer

yarn add babel-polyfill-safer

pnpm add babel-polyfill-safer

Imports

babel-polyfill-safe
wrong
```
const polyfill = require('babel-polyfill-safe')
```
correct
```
import 'babel-polyfill-safe'
```
Used as a side-effect import, no named exports. Usually placed at entry point.

default

wrong

const { default } = require('babel-polyfill-safe')

correct

require('babel-polyfill-safe')

CommonJS require works, but there is no default export.

global._babelPolyfill

wrong

defining global._babelPolyfill manually before import

correct

if (global._babelPolyfill) { /* skip */ }

Internal mechanism; not meant for direct use.

Quickstart

Shows how to safely import the polyfill to avoid duplicate instance errors.

// Ensure you have babel-polyfill installed
// npm install babel-polyfill babel-polyfill-safe

// At the very top of your entry file:
import 'babel-polyfill-safe';

// Or with CommonJS:
require('babel-polyfill-safe');

// Now you can use modern features without worrying about multiple polyfill instances.
// Example:
const fn = () => {};
const promise = Promise.resolve();