If my database has name = 1 and name = 2
If you use name=2 to query. When name=2 exist, data related to that is output
Now I use name=3 to query. Add name=3 when name=3 does not exist
If is used to judge how to write. .
function add(data,col){ MongoClient.connect(Url, function (err, db) { var collection = db.collection(col); collection.findOne({'name':data},function(err, doc) { if(doc) { console.log(doc); db.close(); } else { collection.insertOne({'name':data},function () { db.close(); }); } }); }); }