Javacript: Set or Update a URL/QueryString Parameter, and update URL using HTML history.replaceState()

gistfile1.js

// 2024 Update, use URLSearchParams [https://caniuse.com/urlsearchparams]
export function createQueryString2(name: string, value: string, searchParams: any) {
  const params = new URLSearchParams(searchParams);
  params.set(name, value.toLowerCase());

  return params.toString();
}

// ---- Original 2012 version, when browsers really sucked ----
// Explicitly save/update a url parameter using HTML5's replaceState().
function updateQueryStringParam(param, value) {
  baseUrl = [location.protocol, '//', location.host, location.pathname].join('');
  urlQueryString = document.location.search;
  var newParam = key + '=' + value,
  params = '?' + newParam;

  // If the "search" string exists, then build params from it
  if (urlQueryString) {
    keyRegex = new RegExp('([\?&])' + key + '[^&]*');
    // If param exists already, update it
    if (urlQueryString.match(keyRegex) !== null) {
      params = urlQueryString.replace(keyRegex, "$1" + newParam);
    } else { // Otherwise, add it to end of query string
      params = urlQueryString + '&' + newParam;
    }
  }
  window.history.replaceState({}, "", baseUrl + params);
}

Thanks for the code snippet and sharing your thoughts – but I noted when using the code , updateQueryStringParam() adds a "?" every time, so, here is my solution around this;

export const createQueryString = (key: string, value: string) => {
   		var  urlQueryString = document.location.search,
   		newParam = key + '=' + value,
                      params = '?' + newParam; //replace this line with the one below
   		params = newParam;

   	// If the "search" string exists, then build params from it
   	if (urlQueryString) {
   		let keyRegex = new RegExp('([?&])' + key + '[^&]*');

   		// If param exists already, update it
   		if (urlQueryString.match(keyRegex) !== null) {
params = urlQueryString.replace(keyRegex, "$1" + newParam);//replace this line with the one below
   			params = urlQueryString.replace(keyRegex, newParam);
   		} else {
   			// Otherwise, add it to end of query string
   			params = urlQueryString + '&' + newParam;
   		}
   	}
   	// window.history.replaceState({}, "", baseUrl + params);
   	return params;
}

Add here is a better solution for the same

export function createQueryString2(name: string, value: string, searchParams: any) {
		const params = new URLSearchParams(searchParams);
		params.set(name, value.toLowerCase());

		return params.toString();
	}

the function takes care of repalcing the value of a key if already exists

Thanks @mbuguaMaina, URLSearchParams is definitely the best modern approach. I've updated the original Gist to use your version.