JavaScript: Hidden Subform

hidden_subform.js

var HiddenSubform = {
    update: function(object) {
        switch(object.nodeName) {
            case 'SELECT':
                this.updateSelect(object);
                break;
            case 'INPUT':
                if(object.getAttribute('type') == 'checkbox') {
                    this.updateCheckbox(object);
                }
                break;
        }
    },
    updateCheckbox: function(checkbox) {
        // No ajax call, this should just turn a dom element on or off
        var sel = checkbox.getAttribute('show');
        if(sel) {
            var dom = document.querySelector(sel);
            if(dom) {
                if(checkbox.checked) {
                    removeClass(dom, 'hidden');
                } else {
                    addClass(dom, 'hidden');
                }
            }
        }
    },
    updateSelect: function(select) {
        var selectedIndex = select.options.selectedIndex;
        for (var i = 0; i < select.options.length; i++) {
            var sel = select.options[i].getAttribute('show');
            if (sel) {
                var dom = document.querySelector(sel);
                if (dom) {
                    if (i == selectedIndex) {
                        removeClass(dom, 'hidden');
                    } else {
                        addClass(dom, 'hidden');
                    }
                }
            }
        }
        var url = select.getAttribute('url');
        var form = this.getForm(select);
        if(form && url) {
            // Serialize using the AjaxForm serializer
            var data = AjaxForm.serialize(form);
            microAjax(url, this.callback_response.bind(this), data);
        }
    },
    getForm: function(node) {
        /**
         * Traverse up the tree until we find the parent form
         * @param  {dom} !node The node we are wanting to find the parent of
         * @return {dom}       The form element, or null if none found
         */
        if(!node) {
            return null;
        }
        var par = node.parentNode;
        if(par && par.nodeName == 'FORM') {
            return par;
        }
        return this.getForm(par);
    },
    callback_response: function(json) {
        JsonProcessor.run(json);
    }
};