How can I know the previous value from an autorun dependency?

help
1

Hi,

I need to know the previous value for a document from mongo.
An autorun block is run every time the document is updated.
How can I know the previous value from an autorun dependency ?
Is the following scenario common? What is the common approach?
In angularJs, $watches are executed on a changed and let you know the previous value.

let previousGame = {};

this.autorun(() => {
  let game = this.getGame();
  if (!game) {
    return;
  }
// The above block is because game is null until subscription is ready
// Is there a more elegant way to avoid the above check?

  //Exec some logic here
  //More code

  if (previousGame.player2 && !game.player2) {
    //Player2 quit the game
    
  }

  previousGame = { ...game };

});
2

Use Collection.observeChanges instead.