How to realize that if the data exists, update if it does not exist, delete it in mongo

Update the data whose name is cmdhelp in the test table, if it does not exist, create it

db.test.update(
   { "name": "cmdhelp" },
   { "$set": { "age":1} },
   { upsert: true }
)

update :  modify an existing document or a document in a collection
$set :  Append new fields to existing documents
upsert :  If no document matches the query, create a new document

Updated 1 new record(s) in 17ms