how to add some thing to url by js

1function insertParam(key, value) {
2    key = encodeURIComponent(key);
3    value = encodeURIComponent(value);
4
5    // kvp looks like ['key1=value1', 'key2=value2', ...]
6    var kvp = document.location.search.substr(1).split('&');
7    let i=0;
8
9    for(; i<kvp.length; i++){
10        if (kvp[i].startsWith(key + '=')) {
11            let pair = kvp[i].split('=');
12            pair[1] = value;
13            kvp[i] = pair.join('=');
14            break;
15        }
16    }
17
18    if(i >= kvp.length){
19        kvp[kvp.length] = [key,value].join('=');
20    }
21
22    // can return this or...
23    let params = kvp.join('&');
24
25    // reload page with new params
26    document.location.search = params;
27}
28