I have the following code to insert data into DB - this code has to be executed in a sequential order
Router JS
module.exports = function(app) {
app.get('/registerUser', function(req, res ) {
objuser.userName = 'testuser';
objuser.password = 'password';
objuser.status = true;
registerUser (objuser ); //calls Business.js
res.OK();
res.end ();
});
}
Business.js
var registerUser = function (objuser )
{
userDB.registerUser (objuser ) ; //calls db.js
};
db.js
exports.registerUser = function (objUser )
{
var User = db.model(strCollectionName, UserSchema );
var objSchema = new User(objUser);
objSchema.save(function (err)
{
if (err)
console.error (err);
else
console.log ("registerUser : Data insertion success.");
});
}
In the db.js Im getting error from Mongo if I try to insert duplicate value. I wan to pass the error message to HTML page to display the same. What should I do? I tried
throw Error (err)
But it breaks the server.
Assuming you are using expressjs, I'd make use of the next callback. like so:
app.get('/registerUser', function (req, res, next) {
objuser.userName = 'testuser';
objuser.password = 'password';
objuser.status = true;
registerUser(objuser, function (err) {
if(err) {
//this will be handled by express's errorHandler or whatever you have configured
return next(err);
}
//do whatever you want to do with the response
});
});
If you don't want to make your Business.js call async then you will obviously change this code to a try...catch flow. Node.js apps are happier using async calls though, so a common convention in nodejs apps is to expose a callback using the (err, result) parameters. So your db.js call would be :
exports.registerUser = function (objUser, callback )
{
var User = db.model(strCollectionName, UserSchema );
var objSchema = new User(objUser);
objSchema.save(function (err) {
if (err) return callback(err);
return callback(null, objSchema);
});
}
By now you probably notice that your Business.js call would just be a mediator between your route and your db code...whether you need it or not is up to you.
HTH, Mike
If you are using node.js >= 0.8.x you can use connect-domain middleware that adds new domain functionality to your express/connect application. With doamin module you don't need to pass error up manually. You can simple throw error and it will be passed to error handler automatically.