如何不将一个以上的数据保存到mongodb中的集合中？

Question

如果该集合中已经存在数据，我不想保存其他数据

Answer 1

这是一个简单的实现，用于在Collection中已经存在文档的情况下如何防止编写文档。

Collection.find( {}, (err, docs) => { // By not giving any arguments inside "{}", you tell MongoDB to return all the documents.
    if(docs) {  // If there are any documents already present in the Collection, this will become true and nothing will happen.
        return;
    } else {  // If there's no document already present in the Collection, new document will be added.
        Collection.save(doc);
    }
} );