Для обработки URL я предпочитаю использовать пакет URL .Для твоего случая я сделаю
const url = require('url');
const targetUrl = 'results?condition=Used&year=2010';
const parsedUrl = url.parse(targetUrl, true);
delete parsedUrl.search; // need to delete it so we can construct new query
delete parsedUrl.query.condition; // delete "condition"
console.log(url.format(parsedUrl)); // results?year=2010