Difference between done() and then()

[Jonas Amundsen]

Hi

Is there any difference between using then() and ending the promise chain with done() as opposed to just using done()? I have illustrated the two ways below, for clarity.

foo().then(function (resolution) {

  // ...

}).done();

foo().done(function (resolution) {

  // ...

});

[Stuart Knightley]

Nope, there's no difference between the two.

In the past I have lent towards keeping the handlers in `.then(...)` and ending with just `.done()`

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[Mariusz Nowak]

You can refer to it as to map and forEach in case of arrays.

If you just want to iterate an array, will you use forEach or map? Of course both will work, and you can be ok with map in all cases. but as you know it produces another array, so probably cleaner is to stay with forEach.

Same is with then. In contrary to done, it produces another promise, if you don't needed it, it's cleaner to just use done.

There are also other important implication that comes with then, that is error swallowing (try to crash in callback). If library you're using is not backed with proper error reporting mechanism, then you'll be left with silent exceptions, and trust me, it's last thing you want to deal with.