How does Mongodb save data to ensure the integrity of fields?

for example:
my backend model defines an object, 

user = {
name: required false,
mobile: required true,
email: required false
}

since my name field and email field are not required, I did not send it at the front end, but passed json:

in the following format 
user =  {
mobile: 1118828819
}

the backend receives the json and saves it directly in the MongoDB. When I need to call the user"s information next time, the backend reads the record from the database. However, there is a problem, there are no remaining two fields, which is different from the interface field defined by me and the frontend. How can I solve this problem?

Node.js mongodb
Mar.28,2021

I don't know whether you are using mongodb.js or mongoose.js to connect to mongoDB
if it is mongodb.js, do a null check when creating this user, and save a default value if not.
if it is mongoose.js, you can set the default value when defining Schema, such as

. 
const schema = new Schema({
    name:{
        type:String,
        required:true,
        default:'name'
    },
    //...
});

can I add an empty defult string

@ O'Dou Dou's answer is correct. Mongoose's Schema can use the required attribute to standardize the data, so the data that does not meet the requirements will fail to be stored in mongodb.

however, even if the database is standardized, the front end cannot assume that the data returned by the database is all right, and the front end still needs to validate and tolerate the data returned by the back end. Because the front end and the back end are separate, the front end needs to assume that the back end will go wrong. In fact, the back-end error is also inevitable, because the code is constantly changing, which day the back-end accidentally deleted the required field?

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