.babelrc

{
  "presets": [
    // Determines the polyfills we need based on browser version
    ["@babel/preset-env", {
      // Disable module transformation—we don’t need it in Chrome
      "modules": false,
      "targets": {
        "browsers": ["last 4 Chrome versions"]
      },

      // Trims down babel-polyfill to only the polyfills we need for our supported browsers
      "useBuiltIns": "usage",

      // Explicitly indicate which version of core-js we’re using—required for `useBuiltIns` option
      corejs: 3,
    }],

    // Adds support for JSX
    "@babel/preset-react",
  ],

  "env": {
    "test": {
      // Required for Jest, which runs in node, which doesn’t support ES6 modules
      "plugins": ["@babel/plugin-transform-modules-commonjs"]
    }
  },

  "plugins": [
    // Adds support for @decorators
    // NOTE: Must be before plugin-proposal-class-properties
    // See https://babeljs.io/docs/plugins/transform-decorators/
    ["@babel/plugin-proposal-decorators", {
      "decoratorsBeforeExport": false,
    }],

    // Adds support for static class properties
    // NOTE: Must be after plugin-proposal-decorators
    // See https://babeljs.io/docs/plugins/transform-class-properties/
    "@babel/plugin-proposal-class-properties",

    // Adds support for the spread operator, e.g. `...props`
    // See https://babeljs.io/docs/plugins/transform-object-rest-spread/
    "@babel/plugin-proposal-object-rest-spread",

    "lodash",

    // Adds support for aliases in imports, e.g.
    //     import Foo from 'components/Foo'
    // instead of
    //     import Foo from '../../../Foo'
    // See https://github.com/tleunen/babel-plugin-module-resolver
    ["module-resolver", {
      "alias": {
        "components": "./src/components",
        "src":        "./src",
        "test":       "./test"
      }
    }],
  ]
}