babel-plugin-transform-remove-polyfill

A Babel plugin that removes polyfills and transforms feature detection patterns for modern JavaScript environments. Perfect for targeting evergreen browsers where native APIs are guaranteed to be available.

Features

• 🚀 Removes polyfills - Transforms polyfill fallbacks to use native APIs directly
• 🔍 Eliminates feature detection - Converts typeof checks and conditionals to their known values
• ⚡ Code optimization - Simplifies logical expressions and removes dead code
• 🎯 Built-in API support - Covers 50+ JavaScript built-ins (Object, Array, String, Symbol, etc.)

Install

npm i babel-plugin-transform-remove-polyfill -D
# or
yarn add babel-plugin-transform-remove-polyfill -D

Quick Example

Input:

// Polyfill pattern
var assign = Object.assign || function(target) {
  for (var i = 1; i < arguments.length; i++) {
    var source = arguments[i];
    for (var key in source) {
      if (Object.prototype.hasOwnProperty.call(source, key)) {
        target[key] = source[key];
      }
    }
  }
  return target;
};

Output:

// Native API usage
var assign = Object.assign;

Usage

Basic Setup

Add to your babel.config.json:

{
  "plugins": ["babel-plugin-transform-remove-polyfill"]
}

With Options

{
  "plugins": [
    ["babel-plugin-transform-remove-polyfill", {
      "transform": true
    }]
  ]
}

Transformations

1. Polyfill Removal

Transforms polyfill patterns to use native APIs:

// Before
var isArray = Array.isArray || function(obj) {
  return Object.prototype.toString.call(obj) === '[object Array]';
};

// After
var isArray = Array.isArray;

2. Feature Detection Elimination

Removes typeof checks for known built-ins:

// Before
if (typeof Object.defineProperty === 'function') {
  Object.defineProperty(obj, 'prop', descriptor);
}

// After
Object.defineProperty(obj, 'prop', descriptor);

3. Dead Code Elimination

Removes unreachable code paths:

// Before
if (typeof Symbol !== 'undefined') {
  obj[Symbol.iterator] = function() { return this; };
} else {
  obj.iterate = function() { return this; };
}

// After
obj[Symbol.iterator] = function() { return this; };

Configuration

Enable All Optimizations

{
  "plugins": [
    ["babel-plugin-transform-remove-polyfill", {
      "transform": true
    }]
  ]
}

Granular Control

Enable specific optimizations:

{
  "plugins": [
    ["babel-plugin-transform-remove-polyfill", {
      "transform": {
        "optimize:Object.assign": true
      }
    }]
  ]
}

Custom Global Objects

Add your own global objects to be recognized:

{
  "plugins": [
    ["babel-plugin-transform-remove-polyfill", {
      "globalObjects": ["customGlobal"],
      "globalFunctions": ["customFunction"]
    }]
  ]
}

Advanced Examples

Object.assign Optimization

The optimize:Object.assign option flattens nested Object.assign calls:

// Before
Object.assign(Object.assign({}, defaults), options);

// After (with optimize:Object.assign: true)
Object.assign({}, defaults, options);

hasOwnProperty Modernization

Automatically converts to modern Object.hasOwn:

// Before
Object.prototype.hasOwnProperty.call(obj, prop);

// After
Object.hasOwn(obj, prop);

License

MIT