In your current code, they act the same because console.log('success'); will not fail.
However, if you write something like this...
myPromise.then(function() {
// Some error may happen
throw('An exception that would be caught');
}).catch(function() {
console.log('error');
});
// Is the same as this, the errHandle tries to catch any unhandled error
// from previous result.
myPromise.then(func, null).then(null, errHandle);
myPromise.then(function() {
// Some error may happen
throw('An unhandled exception.');
}, function() {
// This won't log the error if it happens in the
// some error may happen block.
console.log('error');
});
// Is the same as this, the errHandle will handle errors from previous result,
// but it won't handle errs in func.
myPromise.then(func, errHandle)
The second form can't catch that error, while the first can.
Snippet for test:
// An function that may error and throw exception.
function funcThatThrows(test) {
throw(`oops - error in test ${test}`);
}
function errHandler(exception) {
console.log('We got an exception: ', exception);
}
// Expect: We got an exception: oops - error in test 1
Promise.resolve(1).then(funcThatThrows).catch(errHandler);
// Is the same as below, the errHandler tries to catch any unhandled error
// from previous result.
// Expect: We got an exception: oops - error in test 2
Promise.resolve(2).then(funcThatThrows, null).then(null, errHandler);
// If put the function and handler in the same then, the exception won't be caught.
// Expect: Uncaught (in promise) oops - error in test 3
Promise.resolve(3).then(funcThatThrows, errHandler);
