backstory: In chessboardjs you load the board with callback functions for specific events. Chess mechanic that gives me problem is the promotion. I need to hold my callback, prompt a user for a piece he wants to promote to, check if it is a valid move and return('snapback') or execute the move.

Stupid solution: If I prompt with classic

promoPiece = prompt();

everything works, but it looks kinda ugly.

Failed solution: But when I try to create a promise that attaches a callback to my overlay element, to get user click on specific piece I fail(i need to make function async to use promises). I try to get the piece as

async function onDrop(args)
{
  ..code..
  promoPiece = await promoPrompt();
  ..code..
  if(invalid())
  {return 'snapback'}
}

and the promotion mechanic works, but the return snapback statement does not work because now the promise is returned instead of a string and it is not accepted with the chessboardjs...(I assumed, I did not dig into source)

Question: 1)How does prompt differ from my solution? 2)How does it work? 3)How can i create a custom promotion handler for a synchronous callback? 4)Can i use promoPrompt.then(myResolve) syntax without making onDrop() async?