I'm relatively new to Node.js and I need to execute a series of functions one after the other, as they are interdependent. Initially, I opted for the callback function approach where I invoked another callback, essentially creating nested callbacks in sequential order to achieve the desired outcomes.
However, at some point, I came across the concept of Callback Hell and realized that it should be avoided. This left me perplexed about how to utilize promises/ async-await to accomplish the same goal.
Furthermore, I'm puzzled about how promises differ from nested callbacks, considering that in promises, the subsequent promise is executed only after the previous promise is resolved, indicating a similar nested nature.
If anyone could provide guidance on where I might be mistaken, I would greatly appreciate it.
router.route('/addTasks-approve').get(function(req, res) {
if(req.query.text == 'Approved')
{
User.updateMany({'Addtasks.commonID':req.query.id},
{$set: {"Addtasks.$.width" :'250px',
"Addtasks.$.height" :'32px',
"Addtasks.$.background" :'linear-gradient(45deg, #0f3443, #34e89e)',
"Addtasks.$.border_radius" :'10px / 5px',
"Addtasks.$.status" :req.query.text}},
function (error, success) {
if (!error) {
console.log("Approved color set!");
User.findOne({tag:'Admin','Addtasks.commonID':req.query.id},function (error, dataAdmin) {
if (error) {
console.log("error = "+ error);
res.end('{"msg" : "Some error occurred", "status" : 700}');
}
else {
dataAdmin.Addtasks.forEach(element => {
if(element.commonID == req.query.id)
{
User.findOneAndUpdate({tag:'Client','Addtasks.commonID':req.query.id},
{$push: {'Addtasks.$.Bigpaths4Clients':{$each : element.Bigpaths4Clients}},
$set: {"Addtasks.$.background" :'linear-gradient(45deg, #1E6305, #BDFF00)',
"Addtasks.$.status" :'Done'}},
function (error, data) {
if (error) {
console.log("error = "+ error);
res.end('{"msg" : "Unable to add the Task", "status" : 700}');
}
else {
console.log("Addtasks added to Client's dashboard succesfully");
sendMails2Client(data.email, element.topic, 'In Progress', 'Done');
sendMails2User(dataAdmin.email, element.topic, 'Done', 'Approved');
User.findOne({tag:'Admin','Addtasks.commonID':req.query.id},function (error, dataWriter) {
if (error) {
console.log("error = "+ error);
res.end('{"msg" : "Some error occurred", "status" : 700}');
}
else {
sendMails2User(dataWriter.email, element.topic, 'Done', 'Approved');
res.end('{"success" : "success", "status" : 200}');
}
})
}
})
}
});
}
});
}
else {
res.end('{"msg" : "Unable to set the status and color for Approved", "status" : 700}');
}
});
}
})