jQuery - How to remove duplicate parameter on string? (not array)

I've build this JSFiddle to help you out. I've attempted to keep it as vanilla as possible and left comments.

Quickly – This simply parses the parameter string and replaces duplicate parameter names with the last value found. I couldn't tell exactly what you needed from your question; but maybe this will help get you going.

Here's the JSFiddle code for reference:

/**
 * Open up the console to see what's going on
 */

function parse(str) {
    // parse will split the string along the &
    // and loop over the result

    var keyValues, i, len, el, 
        parts, key, value, result;

    result    = {};
    sepToken  = '&';
    keyValues = str.split('&');

    i   = 0;
    len = keyValues.length;

    for(i; i<len; i++) {
        el    = keyValues[i];
        parts = el.split('=');
        key   = parts[0];
        value = parts[1];

        // this will replace any duplicate param 
        // with the last value found
        result[key] = value;
    }

    return result;
}

function serialize(data) {
    // serialize simply loops over the data and constructs a new string

    var prop, result, value;

    result = [];

    for(prop in data) {
        if (data.hasOwnProperty(prop)) {
            value = data[prop];

            // push each seriialized key value into an array
            result.push(prop + '=' + value);
        }
    }

    // return the resulting array joined on &
    return result.join("&");
}

function run() {
    // run this example

    var paramStr, data, result; 

    // paramStr has a duplicate param, value1
    paramStr = 'value1=bla&value1=foop&value2=ble&page=test&value4=blo&test=blu&car=red';
    data     = parse(paramStr);
    result   = serialize(data);

    return result;

}

console.log(run());