text: /**
   * sort url params by keys, and encode uri components
   */
  const obj2urlParams = obj => objKeysSort(obj)
    .map(key => `${key}=${encodeURIComponent(obj[key] || '')}`)
    .join('&');
  
  const objKeysSort = obj => Object.keys(obj).sort();
  
  module.exports = {
    obj2urlParams,
  };
  