function wrapNode(node, wrappertype, wrapperclass){
    /* utility function to wrap a node in an arbitrary element of type "wrappertype"
     * with a class of "wrapperclass" */
    var wrapper = document.createElement(wrappertype)
    wrapper.className = wrapperclass;
    var innerNode = node.parentNode.replaceChild(wrapper,node);
    wrapper.appendChild(innerNode);
    return wrapper
};
function hasClassName(node, class_name) {
    return new RegExp('\\b'+class_name+'\\b').test(node.className);
};
function addClassName(node, class_name) {
    if (!node.className) {
        node.className = class_name;
    } else if (!hasClassName(node, class_name)) {
        var className = node.className+" "+class_name;
        // cleanup
        node.className = className.split(/\s+/).join(' ');
    }
};
function removeClassName(node, class_name) {
    var className = node.className;
    if (className) {
        // remove
        className = className.replace(new RegExp('\\b'+class_name+'\\b'), '');
        // cleanup
        className = className.replace(/\s+/g, ' ');
        node.className = className.replace(/\s+$/g, '');
    }
};