Get URL Parameters (QueryStrings) using Javascript


Nearly all server-side programming languages have built-in functions to retrieve querystring values of a URL. In web browsers you can access the querystring with client-side JavaScript, but there is no standard way to parse out the name/value pairs. So here is a function to return a parameter you specify. The following javascript code snippet facilitates Javascript's built in regular expressions to retrieve value of the key. Optionally, you can specify a default value to return when key does not exist.

function getQuerystring(key, default_)
  if (default_==null) default_="";
  key = key.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");
  var regex = new RegExp("[\\?&]"+key+"=([^&#]*)");
  var qs = regex.exec(window.location.href);
  if(qs == null)
    return default_;
    return qs[1];

The getQuerystring function is simple to use. Let's say you have the following URL:


and you want to get the "author" querystring's value:

var author_value = getQuerystring('author');

Download querystring.js

If you execute code shown in the above line, the author_value will be bloggingdeveloper. The query string is parsed by the regular expression and the value of the author_value parameter is retrieved. The function is smart in a couple of ways. For example, if you have an anchor in your URL like our example URL above does (#top) the getQuerystring() function knows to stop before the # character. Also, if a requested parameter doesn't exist in the query string and the default value is not specified as a function parameter then an empty string is returned instead of a null.

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December 17. 2008 22:19

Cheers matey... Just what I was looking for, and used it perfectly on our new site! Thanks

ChairNut | Reply

December 29. 2008 13:07

FIrst, I'am confused by this line:

key = key.replace(/[\[]/,"\\\[").replace(/[\]]/,"\\\]");

when i understand it , i find there is a bug.
if the key contains chars "(" , ")", the regex is wrong, finally cause
a bug.

wenming wang | Reply

December 29. 2008 13:26

This function does wok well

function getQuerystring2(key, default_)
    if (default_==null)
    var search = unescape(location.search);
    if (search == "")
        return default_;
    search = search.substr(1);
    var params = search.split("&");
    for (var i = 0; i < params.length; i++)
        var pairs = params[i].split("=");
        if(pairs[0] == key)
            return pairs[1];
    return default_;

wenming wang | Reply

January 3. 2009 12:10

<script type="text/javascript">
     setInterval("doSomething()", 5000);

     function doSomething()
           // do something        
</script> yo can use it.

Lida | Reply

January 26. 2009 18:52

Thanks for information.

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September 30. 2009 11:06

Exactly as what I am looking! This is very helpful for my new project. More articles like this please.. Will bookmark your blog.

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October 20. 2009 16:00

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This post was mentioned on Twitter by bloggingdev: Get Querystring with JavaScript - Parse/Get QueryString with Client-Side JavaScript - http://bit.ly/HdUdO

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December 26. 2009 19:27

Yea nice Work !Laughing

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