_.walk

_.mixin({
 
    /*
     * Walk trough every  <key, value> in a given object or array
     * Usage:
     *      var obj = {a: 1, b: 2, c: {d: 3, e: 4}}
     *     _.walk(obj, function(value, key, obj){
     *         console.log(value);
     *     });
     *  //Output: 1, 2, 3, 4
     */
    walk: function(obj, iterator, context){
        _.each(obj, function(value, key){
            if(_.isObject(value)){
                _.walk(value, iterator, context);
            }else{
                iterator.call(context, obj[key], key, obj);
            }
        });
    }
});

Example:

var versionString = '2';
var templateUrlObj = {
  APP: {
    'ADD': 'addurl.html',
    'DEL': 'deleteurl.html'
  },
  USER: {
    'LOGOUT' : 'logout.html'
  }
}

//Add cacheBuster versionString to all the template url's
(function addParamsToUrls(urlObj, param){

    //Walk trough the url templates
    _.walk(urlObj, function(url, key, obj){
        //add versionString
        obj[key] = [
           url, ((url.indexOf('?') === -1) ? '?' : '&' ), 'cacheBuster=' ,versionString 
        ].join('');
    });

})(templateUrlObj, versionString);