NodeJS, Is it a bad practise to return res.json

Question

I\'m building a ExpressJS application with NodeJS. My question is there any performance difference if I do

app.get(\'/test\', function(req, res) {
    fn(functi         


        

Answer 1

Returning an object in a function don't make additional load.

Answer 2

On the contrary, I think many would tell you this sort of idiom is a very sound practice as it makes clear to the reader (often your future self) that you are exiting). What is very nice about the strategy in this particular case is that you can save a bit more code since you now only have a single statement in your conditional branch, which means you can lose some curly braces.

app.get('/test', function(req, res) {
    fn(function(err, data) {
        if (err)  return res.json(400, {
                    error: 1,
                    msg: "some error"
                 });
    ///more code
    });
});

But you asked if there was a performance difference. If there is, I think it would be all but imperceptible.

Answer 3

On your exemple, based on callback function, there is no difference. But what if app.get return a Promise ?

This code will provide an Unhandled rejection Error

app.get('/test')
.then( (data) => 
{ /* do something with your data that can throw a functional error 
for exemple request for a user on your database based on your data */ 
  if (!user) res.json(401, {msg: 'USER NOT FOUND'});
  if (user.someProperty) //will throw an error when user is not found
   res.json(200, {msg: 'USER DID IT'});
})
.catch( (err) => {
  res.json(500, {msg: 'OUTCH'});
  throw(err);
});

This code will not

app.get('/test')
.then( (data) => 
{ /* do something with your data that can throw a functional error 
for exemple request for a user on your database based on your data */ 
  if (!user) return res.json(401, {msg: 'USER NOT FOUND'});
  if (user.someProperty) //will not be evaluate when user is not found
   return res.json(200, {msg: 'USER DID IT'});
})
.catch( (err) => {
  res.json(500, {msg: 'OUTCH'});
  throw(err);
});

When using promise always return ;)