NodeJS MongoDB Callback Hell - node.js

Question

I'm still having trouble with conditionals and database callbacks, I wrote a routing function that querys for a violation object and this is from a form filled out in the client side. I am trying to change the user that owns this violation as an option, I query for that user and return it fine however at the if statement, x != y will always return true because of the nature of how I wrote this. I want it to finish querying, and then hit the conditional. I feel kind of stuck on how to go about this.
if(viol.user != user[0]._id)
That way when I edit the user who owns that violation or object, the user doesn't add the same object to itself over and over again.
app.post('/singleViolation/:violation', isAdmin, function(req, res) {
var violation = req.params.violation;
Violation.findById(violation, function(err, viol){
if (err) throw err;
if (req.body.cause === '') {
req.body.cause = viol.cause;
}
if (req.body.date === '') {
req.body.date = viol.date;
}
if (req.body.location === '') {
req.body.location = viol.location;
}
if(req.body.email === '') {
req.body.email == viol.user;
}
if( req.body.email != '') {
User.find({"local.email" : req.body.email}, function (err, user) {
if (err) {
req.body.email = viol.user;
}
if(viol.user != user[0]._id) {
typeof viol.user;
typeof user[0].id;
console.log(viol.user);
console.log(user[0]._id);
console.log(viol.user === user[0].id);
viol.user = user[0];
viol.save();
user[0].local.violations.push(viol);
Vehicles.findById(viol.vehicle, function(err, veh) {
user[0].local.vehicles.push(veh);
veh.owner = user[0];
veh.save();
user[0].save();
});
}
});
}
viol.cause = req.body.cause;
viol.date = req.body.date;
viol.location = req.body.location;
viol.save();
});
res.json(req.body);
});
app.get('/editViolations/:violations', isAdmin, function(req, res) {
res.render('editViolations.ejs');
});

Answer 1

You need to use Events in order to achieve what you want. Below is just a high-level solution.
Trigger an Event when quering is finished.
Associate the above event to you condition statement.
Trigger another event when you meet your required condition.
Associate this event with your return statement.
Read this good tutplus blog to wrap your head around node event module.

Answer 2

I believe you should first go through the concepts of callback functions and how to avoid callback hell
Below links would help you kick start with callbacks
understanding callback functions
callback hell