Retireving the Current URL

The current page URL can be accessed directly through the native window object:

window.location.href;

This requires no external libraries—standard JavaScript suffices.

Extracting URL Query Parameters

Retrieving specific parameters from the URL query string involves parsing the search portion. The following approach uses a regular expression pattern to match and extract parameter values.

function getQueryParam(paramName) {
    var pattern = new RegExp("(^|&)" + paramName + "=([^&]*)(&|$)");
    var result = window.location.search.substring(1).match(pattern);
    if (result !== null) {
        return decodeURIComponent(result[2]);
    }
    return null;
}

For a URL like http://example.com/page?redirect=dashboard, retrieve the value like this:

var target = getQueryParam('redirect');

Creating a jQuery Plugin Method

Extend jQuery by adding a custom method that wraps the parameter extraction logic:

(function ($) {
    $.getQueryParam = function (paramName) {
        var pattern = new RegExp("(^|&)" + paramName + "=([^&]*)(&|$)");
        var result = window.location.search.substring(1).match(pattern);
        if (result !== null) {
            return decodeURIComponent(result[2]);
        }
        return null;
    };
})(jQuery);

After adding this extension, retrieve parameters using the jQuery syntax:

var target = $.getQueryParam('redirect');

Complete Implementation Example

<script src="jquery-1.7.2.min.js" type="text/javascript"></script>
<script type="text/javascript">
    $(function () {
        // Extend jQuery with custom method
        (function ($) {
            $.getQueryParam = function (paramName) {
                var pattern = new RegExp("(^|&)" + paramName + "=([^&]*)(&|$)");
                var result = window.location.search.substring(1).match(pattern);
                if (result !== null) {
                    return decodeURIComponent(result[2]);
                }
                return null;
            };
        })(jQuery);

        // Extract parameter using jQuery
        var target = $.getQueryParam('redirect');
        console.log(target);
    });
</script>

Handling Character Encoding

When working with non-ASCII characters in URL paarmeters, encoding and decoding methods must match. If parameters are encoded using encodeURI(), decoding must use decodeURIComponent():

Using mismatched encode/decode methods produces garbled text, particularly with Chinese characters.

Alternative Parsing Approach

Another method builds an object containing all query parameters:

function parseQueryString() {
    var params = {};
    var query = window.location.search.substring(1);
    var pairs = query.split('&');
    
    for (var i = 0; i < pairs.length; i++) {
        var separator = pairs[i].indexOf('=');
        if (separator === -1) continue;
        
        var key = pairs[i].substring(0, separator);
        var value = pairs[i].substring(separator + 1);
        params[key] = decodeURIComponent(value);
    }
    return params;
}

var allParams = parseQueryString();
var id = allParams['id'];

This approach collects all parameters into a single object, useful when multiple values need access.