JavaScript update GET query key/value pair and redirect.

redirectWithGetDataChange

function redirectWithGetDataChange(key, value) {
    var getData = window.location.search.substr(1).split("&"),
        getKeyValue = null,
        getKeyChanged = false;

    for (var i=0; i<getData.length; i++) {
        getKeyValue = getData[i].split("=");

        if (getKeyValue[0] == key) {
            getData[i] = key + "=" + value;
            getKeyChanged = true;
        }
    }

    // If the get "key" hasn't been changed then we will take that as a sign
    // showing that the get key doesn't exist in the current URL so we add
    // it ourselves.
    if (! getKeyChanged) {
        getData.push(key + "=" + value);
    }

    window.location.href = window.location.pathname + "?" + getData.join("&");
}