index.js

let env = process.env.BABEL_ENV || process.env.NODE_ENV;
if (env !== 'development' && env !== 'test' && env !== 'production') {
    throw new Error(
        'Using `focus-preset-babel` requires that you specify `NODE_ENV` or ' +
        '`BABEL_ENV` environment variables. Valid values are "development" ' +
        '"test", and "production". Instead, received: ' +
        JSON.stringify(env) +
        '.'
    );
}
let LEGACY_EXPORTS;
if (process.env.LEGACY_EXPORTS) {
    LEGACY_EXPORTS = JSON.parse(process.env.LEGACY_EXPORTS)
} else {
    LEGACY_EXPORTS = false;
}

let LEGACY_LODASH;
if (process.env.LEGACY_LODASH) {
    LEGACY_LODASH = JSON.parse(process.env.LEGACY_LODASH)
} else {
    LEGACY_LODASH = false;
}


let browsers = process.env.BROWSERS || ">1%|last 4 versions|Firefox ESR|not ie < 9";

const plugins = [
    'babel-plugin-transform-decorators-legacy',
    'babel-plugin-transform-class-properties',
    ['babel-plugin-transform-object-rest-spread', { useBuiltIns: true }],
    'babel-plugin-transform-function-bind',
    ['babel-plugin-transform-react-jsx', { useBuiltIns: true }],
    ['babel-plugin-transform-runtime', { helpers: false, polyfill: false, regenerator: true }],
    ['babel-plugin-transform-regenerator', { async: false }],
    'babel-plugin-syntax-dynamic-import'
    // 'babel-plugin-transform-proto-to-assign',
    // ['babel-plugin-transform-es2015-classes', { loose: true }]
];

if (!LEGACY_LODASH) {
    plugins.push('babel-plugin-lodash');
}

if (LEGACY_EXPORTS) {
    plugins.push('babel-plugin-add-module-exports');
}

module.exports = {
    presets: [
        // Latest stable ECMAScript features
        [
            'babel-preset-env',
            {
                targets: {
                    browsers: browsers.split('|'),
                },
                // forceAllTransforms: !!process.env.HOT_RELOAD,
                uglify: !!process.env.HOT_RELOAD || LEGACY_EXPORTS,
                // Enable polyfill transforms
                useBuiltIns: true,
                // Do not transform modules to CJS
                modules: LEGACY_EXPORTS ? 'commonjs' : false
            },
        ],
        'babel-preset-react'
    ],
    plugins,
    env: {
        development: {
            plugins: [
                'babel-plugin-transform-react-jsx-source',
                'babel-plugin-transform-react-jsx-self',
                'react-hot-loader/babel'
            ]
        },
        production: {
            plugins: [
                'transform-react-remove-prop-types'
            ]
        }
    }
};