In Express.js, should I return response or not?

Question

For Express.js 4.x I can't find wether I should return the response (or next function) or not, so:

This:

app.get('/url', (req, res) => {
    res.send(200, { message: 'ok' });
});

Or this:

app.get('/url', (req, res) => {
    return res.send(200, { message: 'ok' });
});

And what is the difference?

Answer 1

I do not agree with the answer above. Sometimes the callback function can return several responses depending on the logic of the app:

router.post("/url", function(req, res) {
// (logic1)
     res.send(200, { response: 'response 1' });
   // (logic2) 
      res.send(200, { message: 'response 2' });
    }})  

This will throw this error:

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

Which can actually be solved with using return . It can also be solved with using if else clauses.

Answer 2

You don't. The (req, res) signature tells express this is the last function in the chain, and it does not expect a return value from this function. You can add a return statement, but it don't "do anything", beyond the JS engine performing some additional (but meaningless) overhead.

Answer 3

It depends.

Calling the res or req callback doesn't mean your routing function is gonna stop working

app.get('/url', (req, res) => {

    if (true) {
        res.send(200, { message: 'ok' });
    }

    const newFunction = () => {
        // stuff useless to your routing function
    }
    newFunction()

});

In here the newFunction() is gonna get called and it's useless, it's gonna impact your server performances.

you better use return res.send(200, { message: 'ok' }); everytime, except if you wanna make a process in the background...

A process typically that can't be expected more than the classical 30 seconds http request. (Me I am making one that takes 4 or 5 hours everyday for example :D)