Appending parameter to URL without refresh

You can use the pushState or replaceState methods, i.e. :

window.history.pushState("object or string", "Title", "new url");

OR

window.history.replaceState(null, null, "?arg=123");

Example with argument:

var refresh = window.location.protocol + "//" + window.location.host + window.location.pathname + '?arg=1';    
window.history.pushState({ path: refresh }, '', refresh);

If anyone wants to add a parameter to a more complex url (I mean, https://stackoverflow.com/questions/edit?newParameter=1), the following code worked for me:

var newurl = window.location.protocol + "//" + window.location.host + window.location.pathname + '?newParameter=1';
window.history.pushState({ path: newurl }, '', newurl);

Hope this helps!

You can also use URL API if you want to add and remove params at the same time:

const url = new URL(window.location.href);
url.searchParams.set('param1', 'val1');
url.searchParams.delete('param2');
window.history.replaceState(null, null, url); // or pushState