Handling Multiple functionalities in Firebase using Nodejs - node.js

Question

Hellow all,
I'm Newbie to Nodejs and Firebase, I need two functionalities to takes place in a single function and also I have written a piece of code it's works fine.
But My question is, the code I have written is the correct way to achieve the multiple functionality or do we have any other alternate method(correct way) to achieve the same functionality.
Doubt :
Retrieving relevant details of project ----> Inside Callback function ----> saving data to another table ----> Inside Callback function ----> Deleting data from table -----> Inside Callback function ----> response
Do we need to write the functionality inside the nested callback function to achieve the output or is there is any other way to achieve it .
// Nodejs Post Function
app.post('/delete_user_request_project/', function (req, res)
{
if (!is_admin_login(req.cookies.login_type))
{
return res.redirect('/');
}
var project_id = req.body.project_id; // Getting the project Id
let del_ref = admin.database().ref("user_request_project/" + project_id); // Targeting the details of the project to fetch that particular data
del_ref.once("value", function (snapshot)
{
var request_project_obj = snapshot.val(); // fetching the details of project
if (request_project_obj != null)
{
let update_ref = admin.database().ref("deleted_user_request_project/" + project_id);
update_ref.set(
request_project_obj // Updating project details to another table
).then(function ()
{
del_ref.remove().then(function () // Deleting the details from project Table
{
return res.status(200).send('success');
});
});
}
else
{
var error = "プロジェクトが存在しない";
req.flash("error", error_message);
return res.send({
status: 'error',
error: error
});
}
});
})
TIA

Answer 1

I would suggest you use the Promise version of the once() method instead of the Callback version, as follows. It will allow you to correctly chain the different promises returned by the asynchronous Firebase method.
app.post('/delete_user_request_project/', function (req, res) {
if (!is_admin_login(req.cookies.login_type)) {
return res.redirect('/');
}
var project_id = req.body.project_id; // Getting the project Id
let del_ref = admin.database().ref("user_request_project/" + project_id); // Targeting the details of the project to fetch that particular data
del_ref.once("value")
.then(function (snapshot) {
var request_project_obj = snapshot.val(); // fetching the details of project
if (request_project_obj != null) {
let update_ref = admin.database().ref("deleted_user_request_project/" + project_id);
return update_ref.set(request_project_obj); // Updating project details to another table
}
else {
throw new Error('request_project_obj null');
}
})
.then(function () {
return del_ref.remove();
})
.then(function () // Deleting the details from project Table
{
return res.status(200).send('success');
})
.catch(function (error) {
if (error.message === 'request_project_obj null') {
var error = "プロジェクトが存在しない";
req.flash("error", error_message);
return res.send({
status: 'error',
error: error
});
} else {
//...
}
})
})