Promise Chain 在结束之前不等待 Promise 解决 [英] Promise Chain not waiting for promises to resolve before ending

问题描述

我试图简化这些:

      passData.savedDBGames.forEach((gameInfo) => {
        return new Promise((resolve, reject) => {
          stats.getPlayersStats(gameInfo.fixtureID).then((playerStats) => {
             playerStatsPromise.push(playerStats);
             console.info('Grab Done');
             resolve();
           });
        });
      });

      Promise.all(playerStatsPromise)
        .then(function () {
          console.info('All Done');
          app.io.emit('admin', 'Admin: done');
          resolve(passData);
        });

据我了解 Promise.all 应该等到 playerStatsPromise 中包含的所有承诺都解决了吗?

To my understanding Promise.all should wait until all of the promises contained in playerStatsPromise have resolved?

那么为什么 All Done 在 Grab Done 之前完成?

So why does All Done finish before Grab Done?

推荐答案

您似乎在构建数组 playerStatsPromise 时引用了未定义的变量 data2.而是使用 map 来构建您的数组，因为这将返回承诺:

You seem to reference an undefined variable data2 when building your array playerStatsPromise. Instead use map to build your array, since that will return the promises:

  var playerStatsPromise = passData.savedDBGames.map((gameInfo) => {
    return new Promise((resolve, reject) => {
      stats.getPlayersStats(gameInfo.fixtureID).then((playerStats) => {
         console.info('Grab Done');
         resolve();
       });
    });
  });

  Promise.all(playerStatsPromise)
    .then(function () {
      console.info('All Done');
      app.io.emit('admin', 'Admin: done');
      resolve(passData);
    });

如果这就是您在第一个代码块中所做的全部工作，您可以简化为:

And if this is all you do in your first code block, you could simplify to:

  var playerStatsPromise = passData.savedDBGames
      .map(gameInfo => stats.getPlayersStats(gameInfo.fixtureID));

  Promise.all(playerStatsPromise)
    .then(function () {
      console.info('All Done');
      app.io.emit('admin', 'Admin: done');
      resolve(passData);
    });

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