index.js

/* eslint-disable global-require */

'use strict';

module.exports = function preset(context, opts = {}) {
  const modules = opts.modules !== undefined ? opts.modules : 'commonjs';

  [
    'safari10',
    'edge',
    'loose',
    'es2016',
    'es2017',
    'es2018',
    'shippedProposals',
  ].forEach((optionName) => {
    if (
      opts[optionName] !== undefined &&
      typeof opts[optionName] !== 'boolean'
    ) {
      throw new Error(
        `Preset modern-browsers '${optionName}' option must be a boolean.`
      );
    }
  });

  if (modules !== false && modules !== 'commonjs') {
    throw new Error(
      "Preset modern-browsers 'modules' option must be 'false' to indicate no modules\n" +
        "or 'commonjs' (default)"
    );
  }

  const edge = opts.edge !== undefined ? opts.edge : true;
  const loose = opts.loose !== undefined ? opts.loose : false;
  const es2018 = opts.es2018 !== undefined ? opts.es2018 : true;
  const es2019 = opts.es2019 !== undefined ? opts.es2019 : true;
  const shippedProposals =
    opts.shippedProposals !== undefined ? opts.shippedProposals : true;
  const supportVariablesFunctionName =
    opts.supportVariablesFunctionName !== undefined
      ? opts.supportVariablesFunctionName
      : true;

  if (opts.esnext !== undefined) {
    throw new Error("Preset modern-browsers 'esnext' option was removed");
  }

  const optsLoose = { loose };

  return {
    plugins: [
      /* es2015 */
      modules === 'commonjs' && [
        require('@babel/plugin-transform-modules-commonjs'),
        optsLoose,
      ],

      edge &&
        supportVariablesFunctionName &&
        require('@babel/plugin-transform-arrow-functions'), // needed for function-name
      edge &&
        supportVariablesFunctionName &&
        require('@babel/plugin-transform-function-name'),

      /* es2018 */
      es2018 &&
        (edge
          ? [
              require('@babel/plugin-proposal-object-rest-spread'),
              { loose, useBuiltIns: true },
            ]
          : require('@babel/plugin-syntax-object-rest-spread')),

      es2018 && [
        require('@babel/plugin-proposal-unicode-property-regex'),
        { useUnicodeFlag: true },
      ],

      es2018 && edge
        ? require('@babel/plugin-proposal-async-generator-functions')
        : require('@babel/plugin-syntax-async-generators'),

      es2019 &&
        (edge
          ? require('@babel/plugin-proposal-optional-catch-binding')
          : require('@babel/plugin-syntax-optional-catch-binding')),

      /* shippedProposals */
      shippedProposals &&
        (edge
          ? require('@babel/plugin-proposal-json-strings')
          : require('@babel/plugin-syntax-json-strings')),
      shippedProposals &&
        require('@babel/plugin-proposal-optional-chaining').default,
      shippedProposals &&
        require('@babel/plugin-proposal-nullish-coalescing-operator').default,
    ].filter(Boolean),
  };
};