var links = document.querySelectorAll('a');
const replaceLinks = () => {
  for(var i = 0; i < links.length; i++) {
    if(links[i].href.indexOf('details.php') > -1) {
      links[i].href = links[i].href.replace(/details.php/g, 'download.php');
    }
  }
};

replaceLinks();