Adding a parameter to the URL with JavaScript

Question

In a web application that makes use of AJAX calls, I need to submit a request but add a parameter to the end of the URL, for example:

Original URL:

Answer 1

/**
* Add a URL parameter 
* @param {string} url 
* @param {string} param the key to set
* @param {string} value 
*/
var addParam = function(url, param, value) {
   param = encodeURIComponent(param);
   var a = document.createElement('a');
   param += (value ? "=" + encodeURIComponent(value) : ""); 
   a.href = url;
   a.search += (a.search ? "&" : "") + param;
   return a.href;
}

/**
* Add a URL parameter (or modify if already exists)
* @param {string} url 
* @param {string} param the key to set
* @param {string} value 
*/
var addOrReplaceParam = function(url, param, value) {
   param = encodeURIComponent(param);
   var r = "([&?]|&)" + param + "\\b(?:=(?:[^&#]*))*";
   var a = document.createElement('a');
   var regex = new RegExp(r);
   var str = param + (value ? "=" + encodeURIComponent(value) : ""); 
   a.href = url;
   var q = a.search.replace(regex, "$1"+str);
   if (q === a.search) {
      a.search += (a.search ? "&" : "") + str;
   } else {
      a.search = q;
   }
   return a.href;
}

url = "http://www.example.com#hashme";
newurl = addParam(url, "ciao", "1");
alert(newurl);

And please note that parameters should be encoded before being appended in query string.

http://jsfiddle.net/48z7z4kx/