Best practice for writing promises and when to promise or callback?

Asked May 19 '20 at 11:28

Active May 19 '20 at 11:35

Viewed 43 times

I am trying to understand promises and from what I can understand, there are numerous way of using them. When do I use a promise and when do I use a callback like in the example below? I would like to know the difference here, since from what I can tell, they do pretty much the same job in this example.

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await req.session.destroy().promise().then((data) => {
        console.log(data);
    }).catch((err) => {
        console.log(err);
    });

2

req.session.destroy((err) => {
    if (err) {
       console.log(err);
    } else {
      console.log('Session successfully destroyed');
   }
});

edited May 19 '20 at 11:35

asked May 19 '20 at 11:28

Gustav Vingtoft

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There are no promises in the second example – Quentin May 19 '20 at 11:30
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The second one is actually a callback-pattern and not a promise-pattern. – Sirko May 19 '20 at 11:31
I see that now, stupid of me. However, my question still stand, since from what I can tell they do the same job correct? – Gustav Vingtoft May 19 '20 at 11:32
They do the same job. Callbacks are the traditional approach. I think most new/updated libraries now at least try to employ the promise-pattern. – Sirko May 19 '20 at 11:33
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Duplicate: https://stackoverflow.com/questions/45041462/node-js-when-to-use-promises-vs-callbacks – Quentin May 19 '20 at 11:35
question is now updated – Gustav Vingtoft May 19 '20 at 11:35
Best practice? When they do the same job, always use the promise. – Bergi May 19 '20 at 13:39

Best practice for writing promises and when to promise or callback?

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