Use an in-memory webpack compiler to get specific files or file trees.

requireThroughWebpack.js

import _ from 'lodash';
import MemoryFileSystem from 'memory-fs';
import webpack from 'webpack';

import webpackConfig from '../../webpack.config';

// This function allows you to do an on-the-fly, in-memory webpack compile starting
// with whatever file entry point you want, and receive back the compiled object.
export default (entry, callback) => {

    let config = _.clone(webpackConfig);

    config.watchOptions = {};
    config.entry.length = 0;
    config.entry[0] = entry;

    const compiler = webpack(config);
    const memFs = compiler.outputFileSystem = new MemoryFileSystem();

    const handleCompilerOutput = err => {
        if (err) {
            console.log('error', err);
            return callback(err);
        }

        const outputPath = `${compiler.options.output.path}/${compiler.options.output.filename}`;
        const packedOutput = memFs.readFileSync(outputPath);

        const compiledObject = eval(packedOutput.toString());
        callback(null, compiledObject);
    };

    if (process.env.NODE_ENV !== 'production') {
        // If we are in dev mode, keep watching for file changes and re-run this.
        compiler.watch({}, handleCompilerOutput);
    } else {
        compiler.run(handleCompilerOutput);
    }
}