How it works...

We can see in the preceding output that whether or not the asynchronous function completes in an error state, the last then callback is executed. This is possible because the catch method doesn't stop the promise chain. It simply catches any error states from the previous links in the chain, and then propagates a new value forward.

The final then is then protected from being bypassed by an error state by this catch. And so, regardless of the fulfillment state of prior links in the chain, we can be sure that the callback of this final then will be executed.