Javascript Resolve' & 'Reject' Callbacks as Part of Producer

In the next video, you’ll learn from Srishti more about the result produced by the producer code.

In the last video, you learned that the result produced by the producer code may either be a:

• Success
  When the result of the producer code is success, the resolve() callback is invoked to resolve the promise object.
• Failure
  When the result of the producer code is failure, the reject() callback is invoked to reject the promise object.

At this point, you know about the internal properties of the promise object and you also know when the resolve() and reject() callbacks are invoked depending on the result of the producer code. Now is the time to look at the relation between the internal properties of the promise object and the resolve() & reject() callbacks. You’ll look at them in the next video with Srishti.

In the last video, you learned the following facts:

1.  If the promise is resolved and the following method is invoked inside the producer code:

resolve(val); // resolving a promise with some value

The properties of the promise object change as:

Status = ‘resolved’

Value = val

Status property is set from ‘pending’ to ‘resolved’ and the Value property is set from undefined to val passed in as an argument while invoking the resolve(val) callback.
 

2.  If the promise is rejected and the following method is invoked inside the producer code:

reject(err); // rejecting a promise with some error

The properties of the promise object change as:

Status = ‘rejected’

Value = err

Status property is set from ‘pending’ to ‘rejected’ and the Value property is set from undefined to err passed in as an argument while invoking the reject(err) callback.

In the next segment, you’ll look at the example you saw earlier which establishes the above fact of resolve() callback changing the internal properties of the promise object.