send/common/assets.js

const genmap = require('../build/generate_asset_map');
const isServer = typeof genmap === 'function';
const prefix = isServer ? '/' : '';
let manifest = {};
try {
  //eslint-disable-next-line node/no-missing-require
  manifest = require('../dist/manifest.json');
} catch (e) {
  // use middleware
}

const assets = isServer ? manifest : genmap;

function getAsset(name) {
  return prefix + assets[name];
}

const instance = {
  get: getAsset,
  setMiddleware: function(middleware) {
    if (middleware) {
      instance.get = function getAssetWithMiddleware(name) {
        const f = middleware.fileSystem.readFileSync(
          middleware.getFilenameFromUrl('/manifest.json')
        );
        return prefix + JSON.parse(f)[name];
      };
    }
  }
};

module.exports = instance;