buildQueryParams.js

function buildQueryParams(params = {}) {
	const arrParams = Object.keys(params);
  if(!arrParams.length) {
  	return '';
  }
	return `?${arrParams.map(param => `${param}=${params[param]}`).join('&')}`;
}

console.log(buildQueryParams()); // ''
console.log(buildQueryParams({})); // ''
console.log(buildQueryParams({a: 'test'})); // '?a=test'
console.log(buildQueryParams({a: 'test', bb: 'testb'})); // ?a=test&bb=testb