How to query MongoDb documents using the indices of embedded arrays - mongodb

Question

I am trying to learn how to use mongo queries to reach deep into a data tree. Specifically, I'm trying to remove the object below {"object": 'to remove'}
{
"_id" : ObjectId("7840f22736341b09154f7ebf"),
"username" : "nmay",
"fname" : "Nate",
"lname" : "May",
"data" : [
{
"monthNum" : 1,
"year" : 2016,
"days" : [
{
"date" : "2016-01-01T06:00:00.000Z",
"type1" : [],
"type2" : []
},
{
"date" : "2016-01-02T06:00:00.000Z",
"type1" : [
{"object": 'to remove'}
],
"type2" : []
}
]
}
]
}
so far I know how to query for the user _id, but I'm not sure how to remove the desired object using the indices in each array. In this example I want to remove data[0].days[1].type1[0]
Here is the query that I have so far:
app.delete('/user/:id/data/:monthIndex/days/:dayIndex/type1/:type1Index', function (req, res, next) {
var monthIndex = parseInt(req.params.monthIndex); // these console the value properly
var dayIndex = parseInt(req.params.dayIndex); // -1 is applied to the parameter to translate to array position
var type1Index = parseInt(req.params.type1Index);
db.users.update(
{ _id: mongojs.ObjectId(req.params.id) },
{ $pull: data.monthIndex.days.dayIndex.type1.type1Index }
);
}
It gives me the error
ReferenceError: data is not defined
Can someone demonstrate how I can pass this query my index parameters to remove the desired object?

Answer 1

Unfortunately, there is no way to remove an array element by its numerical index with a single operation in MongoDB. In order to do this, you need to unset desired element(s) first, and remove the resulting null-valued fields afterwards.
Your code should look something like this:
db.users.update(
{ _id : mongojs.ObjectId(req.params.id) },
{ $unset : { 'data.0.days.1.type1.0' : 1 } }
);
db.users.update(
{ _id : mongojs.ObjectId(req.params.id) },
{ $pull : { 'data.0.days.1.type1' : null } }
);
Edit by #bob: to pass in the parameters you have to build the query string, which is ugly:
var unset = {};
unset['$unset'] = {};
unset.$unset['data.' + req.params.monthIndex + '.days.' + req.params.dayIndex + '.foods.' + req.params.foodIndex] = 1;
db.users.update( { _id : mongojs.ObjectId(req.params.id) }, unset );
var pull = {};
pull['$pull'] = {};
pull.$pull['data.' + req.params.monthIndex + '.days.' + req.params.dayIndex + '.foods'] = null;
db.users.update( { _id : mongojs.ObjectId(req.params.id) }, pull );