create or update querystring

index.js

function paramReplace(uri, key, value) {
        // Find the param with regex
        // Grab the first character in the returned string (should be ? or &)
        // Replace our href string with our new value, passing on the name and delimeter

        var re = new RegExp("[\\?&]" + key + "=([^&#]*)");
        var separator = uri.indexOf('?') !== -1 ? "&" : "?";
        var matches = re.exec(uri);
        var newUri;
        if (matches === null) {
            // if there are no params, append the parameter
            newUri = uri + separator + key + '=' + value;
        } else {
            var delimeter = matches[0].charAt(0);
            newUri = uri.replace(re, delimeter + key + "=" + value);
        }
        return newUri;
    }