Proper promises chaining in Sequelize query

Question

I am working with node/Express, Sequelize and MySQL, and am trying to chain some promises.

I have Project model, and with a hasMany relation I have ProjectImages . I am adding/updating some rows in the images of a specific project ( chainedPromises ), and after this task is finished I want to return this project with all its images:

var chainedPromises = [];
// First resolve this group
data.ProjectImages.forEach((element) => {
    chainedPromises.push(
        models.ProjectImages.upsert(element, {
            where: {
                id: element.id,
            },
        })
    );
});
Promise.all(chainedPromises)
    .then((responses) => {
        responses.map((response) => {
            logJSON(response);
        });
    })
    // Then look for the project and related models
    .then(() => {
        models.Projects.findById(req.params.id, {
            include: [
                {
                    model: models.ProjectImages,
                },
            ],
        })
        // And return it
        .then((result) => {
            logJSON(result);
            return res.send({
                Project: result,
            });
        });
    });

It works, but I think it is a bit like a callback hell.

So, is there a better way to chain this promises?

Also, this way of adding/updating rows in a associate model creates tons of queries. Is there a better way to do this task?

Answer 1

Well, you don't actually chain the promises but nest them.

Proper chaining would look like this:

Promise.all(chainedPromises)
    .then((responses) => {
        responses.map((response) => {
            logJSON(response);
        });
    })
    // Then look for the project and related models
    .then(() => models.Projects.findById(req.params.id, {
        include: [
            {
                model: models.ProjectImages,
            },
        ],
    }))
    // And return it
    .then((result) => {
        logJSON(result);
        return res.send({
            Project: result,
        });
    });

You could alternatively also look into async / await .