{
  "devDependencies": {
    "@babel/preset-react": "^7.10.4",
    "@symfony/webpack-encore": "^0.31.0",
    "node-sass": "^4.14.1",
    "sass-loader": "^9.0.1",
    "ts-loader": "^5.3.0",
    "typescript": "^4.0.2",
    "webpack-notifier": "^1.6.0"
  },
  "dependencies": {
    "@babel/core": "^7.11.6",
    "@types/prop-types": "^15.7.3",
    "@types/react": "^16.9.49",
    "@types/react-dom": "^16.9.8",
    "babel-loader": "^8.1.0",
    "babel-runtime": "^6.26.0",
    "classname": "0.0.0",
    "classnames": "^2.2.6",
    "primeicons": "^4.0.0",
    "primereact": "^5.0.0-rc.1",
    "prop-types": "^15.7.2",
    "react": "^16.13.1",
    "react-dom": "^16.13.1",
    "react-router-dom": "^5.2.0",
    "react-transition-group": "^4.4.1"
  }
}

yarn why v1.22.4
warning package.json: No license field
[1/4] Why do we have the module "core-js"...?
[2/4] Initialising dependency graph...
warning No license field
[3/4] Finding dependency...
[4/4] Calculating file sizes...
=> Found "core-js@2.6.11"
info Reasons this module exists
   - "babel-runtime" depends on it
   - Hoisted from "babel-runtime#core-js"
info Disk size without dependencies: "7.4MB"
info Disk size with unique dependencies: "7.4MB"
info Disk size with transitive dependencies: "7.4MB"
info Number of shared dependencies: 0
Done in 0.85s.

var Encore = require('@symfony/webpack-encore');

// Manually configure the runtime environment if not already configured yet by the "encore" command.
// It's useful when you use tools that rely on webpack.config.js file.
if (!Encore.isRuntimeEnvironmentConfigured()) {
    Encore.configureRuntimeEnvironment(process.env.NODE_ENV || 'dev');
}

Encore
    // directory where compiled assets will be stored
    .setOutputPath('public/build/')
    // public path used by the web server to access the output path
    .setPublicPath('/build')
    // only needed for CDN's or sub-directory deploy
    //.setManifestKeyPrefix('build/')

    /*
     * ENTRY CONFIG
     *
     * Add 1 entry for each "page" of your app
     * (including one that's included on every page - e.g. "app")
     *
     * Each entry will result in one JavaScript file (e.g. app.js)
     * and one CSS file (e.g. app.css) if your JavaScript imports CSS.
     */
    // .addEntry('index', './assets/js/app.js')
    // .addEntry('index','./assets/js/index.tsx')
    .addEntry('index','./assets/js/index.js')
    //.addEntry('page1', './assets/js/page1.js')
    //.addEntry('page2', './assets/js/page2.js')

    // When enabled, Webpack "splits" your files into smaller pieces for greater optimization.
    .splitEntryChunks()

    // will require an extra script tag for runtime.js
    // but, you probably want this, unless you're building a single-page app
    .enableSingleRuntimeChunk()

    /*
     * FEATURE CONFIG
     *
     * Enable & configure other features below. For a full
     * list of features, see:
     * https://symfony.com/doc/current/frontend.html#adding-more-features
     */
    .cleanupOutputBeforeBuild()
    .enableBuildNotifications()
    .enableSourceMaps(!Encore.isProduction())
    // enables hashed filenames (e.g. app.abc123.css)
    .enableVersioning(Encore.isProduction())

    // enables @babel/preset-env polyfills
    .configureBabelPresetEnv((config) => {
        config.useBuiltIns = 'usage';
        config.corejs = 3;
    })

    // enables Sass/SCSS support
    .enableSassLoader()

    // uncomment if you use TypeScript
    .enableTypeScriptLoader()

    // uncomment to get integrity="..." attributes on your script & link tags
    // requires WebpackEncoreBundle 1.4 or higher
    //.enableIntegrityHashes(Encore.isProduction())

    // uncomment if you're having problems with a jQuery plugin
    //.autoProvidejQuery()

    .enableReactPreset()
    // uncomment if you use API Platform Admin (composer req api-admin)
    //.enableReactPreset()
    //.addEntry('admin', './assets/js/admin.js')
;

module.exports = Encore.getWebpackConfig();

.configureBabelPresetEnv((config) => {
        config.useBuiltIns = 'usage';
        config.corejs = 3;
    })