Transforms a promise's value by applying a function to the promise's fulfillment
or rejection value. Returns a new promise for the transformed result.
The then() method registers new fulfilled and rejection handlers with a promise
(all parameters are optional):
-
$onFulfilled will be invoked once the promise is fulfilled and passed
the result as the first argument.
-
$onRejected will be invoked once the promise is rejected and passed the
reason as the first argument.
-
$onProgress (deprecated) will be invoked whenever the producer of the promise
triggers progress notifications and passed a single argument (whatever it
wants) to indicate progress.
It returns a new promise that will fulfill with the return value of either
$onFulfilled or $onRejected, whichever is called, or will reject with
the thrown exception if either throws.
A promise makes the following guarantees about handlers registered in
the same call to then():
- Only one of
$onFulfilled or $onRejected will be called,
never both.
-
$onFulfilled and $onRejected will never be called more
than once.
-
$onProgress (deprecated) may be called multiple times.