Question

what does this code means. Explain each line (briefly)

Book.findOneAndUpdate[{isbn:req.params.isbn},

{$set:{authFName:req .body.authFName,

authLName: req.body.authLName}, {new:true}}

Answer 1

This line of code is used to find and modify the first document that matches the given filter in a MongoDB database

Book.findOneAndUpdate[{isbn:req.params.isbn},

The "Book" is an object that links to the collection in the database.

findOneAndUpdate(filter, update) is the function. the first argument ({isbn:req.params.isbn}) is the filter that is used to find the document to be modified. in this case, where "isbn" equals the isbn parameter in the URL. (req.params) is an object that carries all the parameter in the URL string

#-----

$set:{authFName:req .body.authFName,

authLName: req.body.authLName}

The above line of code is the second parameter of the function. It replaces the value of a field with the specified value.

In this case, authFname is set to value of req.body.authFName, the req.body is an abject that carries the data that is received in the POST request body. and similarly the authLName value

#-----

{new:true}

This is the third parameter to the function. by default, the function returns the old record, by using this parameter it returns the new record.

#----

drop a comment if there's any problem