Dynamic Match Variable Mongodb

I want to be able to pass a dynamic BSON variable to match for mongodb.

Here is what I have tried:

var query = "\"info.name\": \"ABC\"";

and

var query = {
    info: {
        name: "ABC"
    }
}

Neither of these work when passing variable 'query' to match (like below):

$match: {
   query
}

but explicitly passing like below does work:

$match: {
   "info.name": "ABC"
}

from Dynamic Match Variable Mongodb