load.js

const fs = require('fs');
const path = require('path');

function getStat(path) {
  try {
    return fs.statSync(path);
  } catch (e) {
    return null;
  }
}

function fileExists(path) {
  let stat = getStat(path);
  return stat && stat.isFile();
}

function directoryExists(path) {
  let stat = getStat();
  return stat && stat.isDirectory();
}

function* load(directory) {
  let index = path.join(directory, 'index.js');
  // If index.js exists in the directory, halt recursion
  // and let index.js do the rest of the subtree
  if (fileExists(index)) {
    yield index;
    return;
  }
  // Otherwise, load all JS files in the directory, and scan all directories
  let children = fs.readdirSync(directory);
  for (let child of children) {
    let node = path.join(directory, child);
    if (node.endsWith(".js") && fileExists(node)) {
      yield node;
    } else if (directoryExists(node)) {
      for (let file of load(node)) {
        yield file;
      }
    }
  }
}