Appending parameter to URL without refresh

I know this has been asked many times before but answers were not descriptive enough to solve my problem. I don't want to change the whole URL of page. I want to append a parameter &item=brand on button click without refresh.

Using document.location.search += '&item=brand'; makes the page refresh.

Using window.location.hash = "&item=brand"; append without refresh but with a hash # which eliminates the usage/effect of the parameter. I tried to remove the hash after appending but that didn't work.

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This answer and many others suggest the use of HTML5 History API, specifically the history.pushState method, and for old browsers is to set a fragment identifier to prevent page from reloading. But how?

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Assuming the URL is: http://example.com/search.php?lang=en

How can I append &item=brand using HTML5 pushState method or a fragment identifier so the output would be like this: http://example.com/search.php?lang=en&item=brand without a page refresh?

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I hope someone can throw some light on how to use the HTML5 pushState to append a parameter to an existing/current URL. Or alternatively how to set a fragment identifier for the same purpose. A good tutorial, demo or piece of code with a little explanation would be great.

Demo of what I've done so far. Your answers would be greatly appreciated.

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

Modified Medhi answer and this did the trick

const insertParam = (key: string, value: string) => {
    key = encodeURIComponent(key);
    value = encodeURIComponent(value);

    let kvp = window.location.search.substr(1).split('&');
    if (kvp[0] === '') {
        const path = window.location.protocol + "//" + window.location.host + window.location.pathname + '?' + key + '=' + value;
        window.history.pushState({ path: path }, '', path);

    } else {
        let i = kvp.length; let x; while (i--) {
            x = kvp[i].split('=');

            if (x[0] === key) {
                x[1] = value;
                kvp[i] = x.join('=');
                break;
            }
        }

        if (i < 0) { 
            kvp[kvp.length] = [key, value].join('=');
        }

        const refresh = window.location.protocol + "//" + window.location.host + window.location.pathname + '?' + kvp.join('&');  
        window.history.pushState({ path: refresh }, '', refresh);
    }
}

export function getHash(hash: string, key: string): string | undefined {
  return hash
    .split("#")
    .find((h) => h.startsWith(key))
    ?.replace(`${key}=`, "");
}
export function setHash(hash: string, key: string, value: string): string {
  let hashArray = hash.split("#").filter((h) => !h.startsWith(key));
  hashArray.push(`${key}=${value}`);
  return hashArray.length > 0
    ? hashArray.reduce((s1, s2) => `${s1}#${s2}`)
    : "";
}
export function deleteHash(hash: string, key: string): string {
  let hashArray = hash.split("#").filter((h) => !h.startsWith(key));
  return hashArray.length > 0
    ? hashArray.reduce((s1, s2) => `${s1}#${s2}`)
    : "";
}