how to get GET and POST variables with JQuery?

For GET parameters, you can grab them from document.location.search:

var $_GET = {};

document.location.search.replace(/\??(?:([^=]+)=([^&]*)&?)/g, function () {
    function decode(s) {
        return decodeURIComponent(s.split("+").join(" "));
    }

    $_GET[decode(arguments[1])] = decode(arguments[2]);
});

document.write($_GET["test"]);

For POST parameters, you can serialize the $_POST object in JSON format into a <script> tag:

<script type="text/javascript">
var $_POST = <?php echo json_encode($_POST); ?>;

document.write($_POST["test"]);
</script>

While you're at it (doing things on server side), you might collect the GET parameters on PHP as well:

var $_GET = <?php echo json_encode($_GET); ?>;

Note: You'll need PHP version 5 or higher to use the built-in json_encode function.

Update: Here's a more generic implementation:

function getQueryParams(qs) {
    qs = qs.split("+").join(" ");
    var params = {},
        tokens,
        re = /[?&]?([^=]+)=([^&]*)/g;

    while (tokens = re.exec(qs)) {
        params[decodeURIComponent(tokens[1])]
            = decodeURIComponent(tokens[2]);
    }

    return params;
}

var $_GET = getQueryParams(document.location.search);

There's a plugin for jQuery to get GET params called .getUrlParams

For POST the only solution is echoing the POST into a javascript variable using PHP, like Moran suggested.

Or you can use this one http://plugins.jquery.com/project/parseQuery, it's smaller than most (minified 449 bytes), returns an object representing name-value pairs.

With any server-side language, you will have to emit the POST variables into javascript.

.NET

var my_post_variable = '<%= Request("post_variable") %>';

Just be careful of empty values. If the variable you attempt to emit is actually empty, you will get a javascript syntax error. If you know it's a string, you should wrap it in quotes. If it's an integer, you may want to test to see if it actually exists before writing the line to javascript.

Here's something to gather all the GET variables in a global object, a routine optimized over several years. Since the rise of jQuery, it now seems appropriate to store them in jQuery itself, am checking with John on a potential core implementation.

jQuery.extend({
    'Q' : window.location.search.length <= 1 ? {}
        : function(a){
            var i = a.length, 
                r = /%25/g,  // Ensure '%' is properly represented 
                h = {};      // (Safari auto-encodes '%', Firefox 1.5 does not)
            while(i--) {
                var p = a[i].split('=');
                h[ p[0] ] = r.test( p[1] ) ? decodeURIComponent( p[1] ) : p[1];
            }
            return h;
        }(window.location.search.substr(1).split('&'))
});

Example usage:

switch ($.Q.event) {
    case 'new' :
        // http://www.site.com/?event=new
        $('#NewItemButton').trigger('click');
        break;
    default :
}

Hope this helps. ;)

You can try Query String Object plugin for jQuery.

Keep it simple

replace VARIABLE_KEY with the key of the variable to get its value

 var get_value = window.location.href.match(/(?<=VARIABLE_KEY=)(.*?)[^&]+/)[0];