How to get values ​​for each element in an array?

Question

JavaScript

You need to get all the tags and their data:

tagsController.get = function(req, res, next) {
  tags.getTags(0, -1, function(err, tags) {
    if (err) {
      return next(err);
    }

    var data = {
      tags: tags,
      title: '#'
    };
    res.render('tags', data);
  });
};

We turn to the function getTagsand get the tags, as well as the values ​​for each of them:

Tags.getTags = function(start, stop, callback) {
    db.getSetMembers('tags:id', function(err, tags) {
      if (err) {
        return callback(err);
      }

      // console.log(tags) = [ '1', '2', '3' ]
      
      tags.forEach(function(tag) {
        async.parallel({
          id: function(next) {
            db.getObjectField('tag:' + tag, 'id', next);
          },
          tagname: function(next) {
            db.getObjectField('tag:' + tag, 'tagname', next);
          },
          tagslug: function(next) {
            db.getObjectField('tag:' + tag, 'tagslug', next);
          }
        }, function (err, results) {
          if (err) {
            return callback(err);
          }

          callback(null, results);
        });
      });

    });
  };

In the end, it should look something like this:

"data.tags":[{"id":1,"tagname":"","tagslug":""},{"id":2,"tagname":"","tagslug":""},{"id":3,"tagname":"","tagslug":""}]

But it gives an error Can't set headers after they are sent.
How to do it right?

Answer 1

In my opinion, you screwed up with async. Doesn't the callback fire before the foreach completes?
In addition, they also write to you that you can’t send headers if something has already gone.