垃圾回收的原理

 groot.createElement = function (html, id) {
        groot.dynamic[id] = id;
        return $(html).append("<input type=‘hidden‘ id=\"" + id + "\">")
    }

 function _collection() {//垃圾回收
        if (_collect) {
            _collect = false;
            groot.asyn(function () {
                for (var id in  groot.dynamic) {
                    if ($("#" + id).length <= 0) {
                        delete  groot.vms[id];
                        delete  groot.dynamic[id];
                    }
                }
                _collect = true;
            })
        }
    }