如何从insertmany的动态构建表单字段返回数据

Im building a form in ejs based on files read from a sourcefolder. Each file will generate a number of fields in a form. The user can add metadata to each file and on submitting the entire form the data should be saved in mongodb. So how do I define the names in the fields so that I ideally could pass the entire req.body directly into mongodb like in this question: Im building a form in ejs based on files read f