regex as $filter in projection

Question

I\'m trying to find (using a regexp) an array field and returns that element only

This is my data

  [
 {
\"_id\": \"56d6e8bbf7404bd80a017edb\",
\"nam         


        

Answer 1

According this issue Use $regex as the expression in a $cond, the $regex could NOT be used with cond for current mongo version.

Maybe you can try this one, filter the area3 through $match, then get all matched tags through $group, then remove the _id through $project.

caseNote.aggregate([{$unwind: '$tags'},
               {$match: {tags: /area3/}},
               {$group: {_id: null, tags: {$push: '$tags'}}},
               {$project: {tags: 1, _id: 0}}])
    .exec(function(err, tags) {
        if (err)
            console.log(err);
        else
            console.log(tags);
    });

Results:

{ "tags" : [ "C area3", "b_area3" ] }