singleSubDoc.js

models.util = {
  singleSubDoc: function(schema, virtualName) {
    var realName = '_' + virtualName;
    schema.virtual(virtualName)
      .get(function() {
        if(this[realName].length) return this[realName][0];
        else return null;
      })
      .set(function(value) {
        this[realName] = [value];
      });
    ;
  }
};

models.SchemaWithSingleLocation = new Schema({

  _location: [Location],

});
models.util.singleSubDoc(models.SchemaWithSingleLocation, 'location');