how to handle promises in this code refactoring

Question

I am refactoring some code that was using a Promise-Mysql library. I am now porting it to Mysql2 library. So far so good but I need help on a piece of code that is working with promises (I am not yet so good with promises).

The original code:

Promise.all([
        db.query("UPDATE gantt_tasks SET text = ?, start_date = ?, duration = ?, progress = ?, parent = ? WHERE id = ?",
            [task.text, task.start_date, task.duration, task.progress, task.parent, sid]),
        updateOrder(sid, target)
    ])
        .then(function (result) {
            sendResponse(res, "updated");
        })
        .catch(function (error) {
            sendResponse(res, "error", null, error);
        });
    });

has become:

con1.execute("UPDATE gantt_tasks SET text = ?, start_date = ?, duration = ?, progress = ?, parent = ? WHERE id = ?",
        [task.text, task.start_date, task.duration, task.progress, task.parent, sid], function (err, result, fields) {
            //if (err) throw err;
            if (err) { sendResponse(res, "error", null, error); }
            updateOrder(sid, target);
            sendResponse(res, "updated");
        });

sendResponse is the following:

function updateOrder(taskId, target) {
    var nextTask = false;
    var targetOrder;

    target = target || "";

    if (target.startsWith("next:")) {
        target = target.substr("next:".length);
        nextTask = true;
    }

    return db.query("SELECT * FROM gantt_tasks WHERE id = ?", [target])
        .then(function (result) {
            if (!result[0])
                return Promise.resolve();

            targetOrder = result[0].sortorder;
            if (nextTask)
                targetOrder++;

            return db.query("UPDATE gantt_tasks SET sortorder = sortorder + 1 WHERE sortorder >= ?",[targetOrder])
                .then(function (result) {return db.query("UPDATE gantt_tasks SET sortorder = ? WHERE id = ?",[targetOrder, taskId]); });
        });
}

My question is: how do I change the return Promise.resolve();? In my code there is not a promise anymore...

Answer 1

Modernized:

async function updateOrder(taskId, target = "") {

  let nextTask = false;

  if (target.startsWith("next:")) {
    target = target.substr("next:".length);
    nextTask = true;
  }

  const result = await db.query("SELECT * FROM gantt_tasks WHERE id = ?", [target]);
  if (!result[0]) return;

  let targetOrder = result[0].sortorder;
  if (nextTask) {
    targetOrder++;
    await db.query("UPDATE gantt_tasks SET sortorder = sortorder + 1 WHERE sortorder >= ?",[targetOrder]);
    await db.query("UPDATE gantt_tasks SET sortorder = ? WHERE id = ?",[targetOrder, taskId]); });
  }

}

async functions always return a promise, so this also fulfills your original requirement.

You should probably use a transaction for this though.