Стася

let re = new RegExp(variable + "=" + ".*?(?=&|$)");
const result = url.replace(re, variable + "=" + newData);

let url = 'http://localhost/?a=1&b=2&test=Y&clear=allcache';

let re = /(\?|&)(.*?)\=(.*?)(?=&|$)/g;

const newdata = {
   test: 333,
   clear: 4444
};

function changeURL(url, keys) {
   return url.replace(re, (a,prefix,key,val)=>{
     if( keys[key] )
       return prefix+key+"="+keys[key];
     return prefix+key+"="+val;
   });
}

url = changeURL(url, newdata);
console.log(url);