How do I return my data from a function?

Question

I've written a small database function that gets some data from the DB and puts it into the format that I want, but I'm having difficulties returning the data to display it with Express. The database function is as follows:

function getAllEvents(req, res, next) {
  db.any('select * from sensors, events where sensors.sensorid = events.sensorid')
    .then(function (data) {
        var final = [];

        data.forEach(function(datas){
            if (!final[datas.sensorid]){
                final[datas.sensorid] = {};
            }
            if (!final[datas.sensorid].name){
                final[datas.sensorid].name = datas.name;
                final[datas.sensorid].signatures = {};
            }
            if (!final[datas.sensorid].signatures[datas.signature]){
                final[datas.sensorid].signatures[datas.signature] = {};
                final[datas.sensorid].signatures[datas.signature].id = "sen" + datas.sensorid + "sig" + datas.signature;
                final[datas.sensorid].signatures[datas.signature].signature = datas.signature;
                final[datas.sensorid].signatures[datas.signature].message = datas.message;
                final[datas.sensorid].signatures[datas.signature].events = {};
            }

            final[datas.sensorid].signatures[datas.signature].events[datas.eventid] = datas;
        })

        return final;

    })
    .catch(function (err) {
      console.log("Something went wrong! ", err)
    });
}

And the router function to call it is this:

router.get('/events', function(req, res, next) {
    db.getAllEvents(function(err, data){
        res.render('events', { data: data });
    });
});

I think the router function is waiting indefinitely for the data though as I get no errors but the page never loads. What am I doing wrong?

Answer 1

What am I doing wrong?

This code:

router.get('/events', function(req, res, next) {
    db.getAllEvents(function(err, data){
        res.render('events', { data: data });
    });
});

is ok besides the fact that you are not checking for errors. Notice that getAllEvents is expecting a function as an argument.

now Let's look at your getAllEvents function prototype

function getAllEvents(req, res, next) {

It is simply not correct and should have been something like

function getAllEvents(callback) {

Then you would be able to call the callback and "return" the result like this

return callback(null,data);

or if an error occurred during you database connection pass the error to the callback

return callback(err);