So I have this array of objects called "items":
and for each object, I want to find the same object in mongodb using the "baseId" in the Base Document, and then update the "jumlahTerjual" amount by +1, this is the "Base Document":

I've tried this method but got an error called "jumlahTerjual is not defined":

How can I update it using findByIdAndUpdate correctly? Any answer will be so much appreciated.
Assuming the jumlahTerjual key exists for each object in you base document,
when you want to increment it (by any custom value), try:
items.map(item => {
return Base.findByIdAndUpdate(item.baseId, {$inc: { jumlahTerjual: 1 }}, function(error, counter) {
if(error)
return next(error);
doc.testvalue = counter.seq;
next();
})
})
Use the $inc operator instead of { jumlahTerjual: jumlahTerjual + 1 } as the update object. Because, currently the interpreter tries to find a local variable called jumlahTerjual which is being incremented by 1 and being assigned to the key in the object found by mongoose. Because we haven't defined a local variable for jumlahTerjual that is why you get the undefined error.
Because you only want to increment, instead of changing the value in the mongoDB record with a new value just use the $inc operator.