node模糊查询mongoDB典型代码1：
包含ss_key
 MGclient.connect(MGurl).then((conn) => {
        var str = "^.*" + ss_key + ".*$";
        var reg = new RegExp(str);
        const cur_DB = conn.db("test");
       var query_obj ={ $and: [{ doc_type: "JXCG" }, { XX_name: { $regex: reg } }] }

node模糊查询mongoDB典型代码2：
以"*年级"开头
 var CUsemester = Q_obj["semester"];    
        var str = "^.年级";
        var reg = new RegExp(str);
    var query_obj = {$and:[{ semester: CUsemester },{TC:{$regex:reg}}]};