code: function isJavaScriptFile(filepath) {
    if (!fs.statSync(filepath).isFile()) {
      return false;
    }
    if (path.basename(filepath) === 'index.js') {
      return false;
    }
    return filepath.slice(-3) === '.js';
  }
docs: Return true if the file is a `.js` file.
  
  @param {String} filepath
  @return {Boolean}