如何更新在云代码中同步的解析对象然后检查它是否成功？

你只需要使用异步/等待：

Parse.Cloud.define('myFunction', async req => {
  const GameScore = Parse.Object.extend("GameScore");
  const gameScore = new GameScore();

  gameScore.set("score", 1337);
  gameScore.set("playerName", "Sean Plott");
  gameScore.set("cheatMode", false);
  gameScore.set("skills", ["pwnage", "flying"]);

  await gameScore.save();

  // Now let's update it with some new data. In this case, only cheatMode and score
  // will get sent to the cloud. playerName hasn't changed.
  gameScore.set("cheatMode", true);
  gameScore.set("score", 1338);

  await gameScore.save();
});