Why extend jQuery? What would be the benefit of extending jQuery vs just having a global function?

function qs(key) {
    key = key.replace(/[*+?^$.\[\]{}()|\\\/]/g, "\\$&"); // escape RegEx meta chars
    var match = location.search.match(new RegExp("[?&]"+key+"=([^&]+)(&|$)"));
    return match && decodeURIComponent(match[1].replace(/\+/g, " "));
}

http://jsfiddle.net/gilly3/sgxcL/

An alternative approach would be to parse the entire query string and store the values in an object for later use. This approach doesn't require a regular expression and extends the window.location object (but, could just as easily use a global variable):

location.queryString = {};
location.search.substr(1).split("&").forEach(function (pair) {
    if (pair === "") return;
    var parts = pair.split("=");
    location.queryString[parts[0]] = parts[1] &&
        decodeURIComponent(parts[1].replace(/\+/g, " "));
});

http://jsfiddle.net/gilly3/YnCeu/

This version also makes use of Array.forEach(), which is unavailable natively in IE7 and IE8. It can be added by using the implementation at MDN, or you can use jQuery's $.each() instead.

JQuery jQuery-URL-Parser plugin do the same job, for example to retrieve the value of search query string param, you can use

$.url().param('search');

This library is not actively maintained. As suggested by the author of the same plugin, you can use URI.js.

Or you can use js-url instead. Its quite similar to the one below.

So you can access the query param like $.url('?search')

Found this gem from our friends over at SitePoint. https://www.sitepoint.com/url-parameters-jquery/.

Using PURE jQuery. I just used this and it worked. Tweaked it a bit for example sake.

//URL is http://www.example.com/mypage?ref=registration&[email protected]

$.urlParam = function (name) {
    var results = new RegExp('[\?&]' + name + '=([^&#]*)')
                      .exec(window.location.search);

    return (results !== null) ? results[1] || 0 : false;
}

console.log($.urlParam('ref')); //registration
console.log($.urlParam('email')); //[email protected]

Use as you will.

This isn't my code sample, but I've used it in the past.

//First Add this to extend jQuery

    $.extend({
      getUrlVars: function(){
        var vars = [], hash;
        var hashes = window.location.href.slice(window.location.href.indexOf('?') + 1).split('&');
        for(var i = 0; i < hashes.length; i++)
        {
          hash = hashes[i].split('=');
          vars.push(hash[0]);
          vars[hash[0]] = hash[1];
        }
        return vars;
      },
      getUrlVar: function(name){
        return $.getUrlVars()[name];
      }
    });

    //Second call with this:
    // Get object of URL parameters
    var allVars = $.getUrlVars();

    // Getting URL var by its name
    var byName = $.getUrlVar('name');

I wrote a little function where you only have to parse the name of the query parameter. So if you have: ?Project=12&Mode=200&date=2013-05-27 and you want the 'Mode' parameter you only have to parse the 'Mode' name into the function:

function getParameterByName( name ){
    var regexS = "[\\?&]"+name+"=([^&#]*)", 
  regex = new RegExp( regexS ),
  results = regex.exec( window.location.search );
  if( results == null ){
    return "";
  } else{
    return decodeURIComponent(results[1].replace(/\+/g, " "));
  }
}

// example caller:
var result =  getParameterByName('Mode');

Building on @Rob Neild's answer above, here is a pure JS adaptation that returns a simple object of decoded query string params (no %20's, etc).

function parseQueryString () {
  var parsedParameters = {},
    uriParameters = location.search.substr(1).split('&');

  for (var i = 0; i < uriParameters.length; i++) {
    var parameter = uriParameters[i].split('=');
    parsedParameters[parameter[0]] = decodeURIComponent(parameter[1]);
  }

  return parsedParameters;
}

function parseQueryString(queryString) {
    if (!queryString) {
        return false;
    }

    let queries = queryString.split("&"), params = {}, temp;

    for (let i = 0, l = queries.length; i < l; i++) {
        temp = queries[i].split('=');
        if (temp[1] !== '') {
            params[temp[0]] = temp[1];
        }
    }
    return params;
}

I use this.

Written in Vanilla Javascript

     //Get URL
     var loc = window.location.href;
     console.log(loc);
     var index = loc.indexOf("?");
     console.log(loc.substr(index+1));
     var splitted = loc.substr(index+1).split('&');
     console.log(splitted);
     var paramObj = [];
     for(var i=0;i<splitted.length;i++){
         var params = splitted[i].split('=');
         var key = params[0];
         var value = params[1];
         var obj = {
             [key] : value
         };
         paramObj.push(obj);
         }
    console.log(paramObj);
    //Loop through paramObj to get all the params in query string.