Can I use '$set' on embedded document when use variable as filed name in MongoDB?

Question

I want to use '$set' to update an embedded document, but the field is a variable.

Say I have a document like:

{'_id': ObjectID,
 'people': {
     'A': {'age': 20}
 }
}

Now I want to add a new person to people. I can use $set: {'people.B':{'age': 25}, but what if the name(instead B) is a variable?

I am using Node.js 5.1 and 'mongodb' driver.

Answer 1

You need to build your query dynamically using the [] operator.

var b = 'B';
var update = {};
update['people.' + b] = { 'age': 25 };
db.collection.update({}, { '$set': update })