Just Questions about Java Script

[TimeKeyRoll]

Hi!Why we are using promise here. If incase it gets failed listener has try Catch. so what makes us use Promise here. I mean I understand Promise either gives us resolve or reject. But either way it will pass or fail if Promise is not there. Right?
Anyone with a good explanation would be highly Appreciated.

[othaime-en]

Hey @MasterofBlockchain we are using a promise here just to make sure we catch the event being emmitted. And to be clear, the try catch doesn't helps us in listening because if the listener doesn't catch the event, the try...catch block never gets executed. And yes, your code might still run without setting up the promise but just to be safe, and to make sure that we catch the event being emitted after we set up the listener. Sometimes the blockchain moves too fast such that we might miss the event when it gets emitted so using a promise acts as a safeguard to make sure that either way, we still catch the event with our listener. After which, execution moves to the try...catch block

[TimeKeyRoll]

Sometimes the blockchain moves too fast such that we might miss the event when it gets emitted so using a promise acts as a safeguard to make sure that either way, we still catch the event with our listener.

If blockchain have or saves all the data how come we could miss the event @othaime-en ? why not it gives us assurance that it will be emitted?
AND still questions remains there how Promise is helping us to get it emitted? :/

[krakxn]

@MasterofBlockchain "If blockchain have or saves all the data how come we could miss the event?" Solely in volatile conditions, only serves as a precaution. Because if it is included in the mined block, as you thought, then it is essentially immutable (after 6 blocks).

"how Promise is helping us to get it emitted? :/" raffle.once (i.e. the event listener) is encapsulated inside the Promise block, and is only resolved (i.e. resolves) if the try-catch does not lead to an error (i.e. rejects).

Hence, the Promise serves like a conditional for the event listener (i.e. either the listener being resolved or rejected). Without the Promise, there is no conditional for the event listener.

[krakxn]

"listener has try Catch" In the try-catch, the try block has no functionality whatsoever, only the catch block is used, and serves to "catch" (also rejects for the promise) any error caught on evaluation. Additionally, even if the try block contained some logic, it is not inclusive of the listener.

Therefore, the promise checks whether the listener itself resolves or rejects.

Of course, you can also do a big try block but promises are more versatile.

[TimeKeyRoll]

ok! thanks man.