How to dynamically $set a subdocument field in mongodb? [duplicate]

Answer 1

Figured this out.

Essentially, you need to construct a 'placeholder' object of the sub-document you're trying to update before running the query, like so:

var projectID = 'JKS78678923SDFD678';

var key = 'Three';
var value = 'Three';

var placeholder = {};
placeholder['options.' + key] = value;

Teams.findAndModify({
    query: {
        projectID:mongojs.ObjectId(projectID)
    },
    update: {
        $set : placeholder
    },
    upsert: true,
    multi: false,
    new: true
},
function(error, result, lastErrorObject){

    console.log(result);

});

This updates any fields that already exist, and creates the field/value pair if it didn't already exist.