Rethrowing error in promise catch

Question

I found the following code in a tutorial:

promise.then(function(result){
    //some code
}).catch(function(error) {
    throw(error);
});

I\'m

Answer 1

There is no important difference if you leave out the catch method call completely.

The only thing it adds is an extra microtask, which in practice means you'll notice the rejection of the promise later than is the case for a promise that fails without the catch clause.

The next snippet demonstrates this:

var p;
// Case 1: with catch
p = Promise.reject('my error 1')
       .catch(function(error) {
          throw(error);
       });

p.catch( error => console.log(error) );
// Case 2: without catch
p = Promise.reject('my error 2');

p.catch( error => console.log(error) );

Note how the second rejection is reported before the first. That is about the only difference.