server.js

var fs = require('fs');
var path = require('path');
var express = require('express');
var rollup = require('rollup-endpoint');
var babel = require('rollup-plugin-babel');
var uglify = require('rollup-plugin-uglify');
var replace = require('rollup-plugin-replace');
var commonjs = require('rollup-plugin-commonjs');
var nodeResolve = require('rollup-plugin-node-resolve');
var rewrite = require('express-urlrewrite');

var app = express();
var port = process.env.PORT || 8080;
var env = process.env.NODE_ENV;

var plugins = [
  nodeResolve({
    jsnext: true
  }),
  babel({
    babelrc: false,
    exclude: 'node_modules/**',
    plugins: ["external-helpers"],
    presets: [
      ["latest", {
        "es2015": {
          "modules": false
        },
        "es2016": false,
        "es2017": false
      }]
    ],
    env: {
      "commonjs": {
        "plugins": [
          ["transform-es2015-modules-commonjs", { "loose": true }]
        ]
      }
    }
  }),
  replace({
    'process.env.NODE_ENV': JSON.stringify(env)
  }),
  commonjs(),
  uglify({
    compress: {
      pure_getters: true,
      unsafe: true,
      unsafe_comps: true,
      warnings: false,
    }
  })
];

app.get(
  '/__build__/Dropbox-sdk.min.js',
  rollup.serve({
    entry: path.resolve(__dirname, '../../src/index.js'),
    plugins: plugins,
    generateOptions: {
      format: 'umd',
      moduleName: 'Dropbox'
    }
  })
);

app.get(
  '/__build__/DropboxTeam-sdk.min.js',
  rollup.serve({
    entry: path.resolve(__dirname, '../../src/team/index.js'),
    plugins: plugins,
    generateOptions: {
      format: 'umd',
      moduleName: 'DropboxTeam'
    }
  })
);

fs.readdirSync(__dirname).forEach(function (file) {
  if (fs.statSync(path.join(__dirname, file)).isDirectory()) {
    app.use(rewrite('/' + file + '/*', '/' + file + '/index.html'));
  }
});

app.use(express.static(__dirname));
app.use('/__dist__', express.static(path.resolve(__dirname, '../../dist')));

app.listen(port, function () {
  console.log("Express server listening on port " + port );
});