How can I add or update a query string parameter?

Question

With javascript how can I add a query string parameter to the url if not present or if it present, update the current value? I am using jquery for my client side development

Answer 1

Java script code to find a specific query string and replace its value *

('input.letter').click(function () {
                //0- prepare values
                var qsTargeted = 'letter=' + this.value; //"letter=A";
                var windowUrl = '';
                var qskey = qsTargeted.split('=')[0];
                var qsvalue = qsTargeted.split('=')[1];
                //1- get row url
                var originalURL = window.location.href;
                //2- get query string part, and url
                if (originalURL.split('?').length > 1) //qs is exists
                {
                    windowUrl = originalURL.split('?')[0];
                    var qs = originalURL.split('?')[1];
                    //3- get list of query strings
                    var qsArray = qs.split('&');
                    var flag = false;
                    //4- try to find query string key
                    for (var i = 0; i < qsArray.length; i++) {
                        if (qsArray[i].split('=').length > 0) {
                            if (qskey == qsArray[i].split('=')[0]) {
                                //exists key
                                qsArray[i] = qskey + '=' + qsvalue;
                                flag = true;
                                break;
                            }
                        }
                    }
                    if (!flag)//   //5- if exists modify,else add
                    {
                        qsArray.push(qsTargeted);
                    }
                    var finalQs = qsArray.join('&');
                    //6- prepare final url
                    window.location = windowUrl + '?' + finalQs;
                }
                else {
                    //6- prepare final url
                    //add query string
                    window.location = originalURL + '?' + qsTargeted;
                }
            })
        });