Javascript para repassar parâmetros UTM

document.addEventListener("DOMContentLoaded", function(){
   var url_ = location.href;
   var params = url_.substring(url_.indexOf("?"));

   if(~params.indexOf("?utm")){
      var as = document.querySelectorAll("a");
      for(var x=0; x<as.length; x++){
         as[x].href = as[x].href+params;
      }
   }
});