Node.js Firestore异步函数无法返回MessageEmbed数组问题排查

我用Firebase查询用户处罚记录，调用异步函数CheckHistory时已经用了await，但函数没返回预期的MessageEmbed数组，控制台打印出[AsyncFunction: CheckHistory]。相关信息如下：

1. 控制台输出 #

[AsyncFunction: CheckHistory]

2. 调用代码 #

let hist = await CheckHistory(id);
console.log(CheckHistory);

3. 函数代码 #

async function CheckHistory(user){
  CheckBan(user);
  let historyArray = [];

  const colRef = db.collection('punishments')
  colRef.where('user', '==', user).get().then(async querySnapshot => {
    length = querySnapshot.size;
    if (querySnapshot.empty){
      console.log(querySnapshot.size)
      return 0;
    } else {
      let docs = querySnapshot.docs;
      for (let documentSnapshot of docs) {
        const revoke = documentSnapshot.get('revoke')

        let active = documentSnapshot.get('active')
        if (active = true){
          active = "Active"
        } else {
          active = `Revoked for ${revoke}`
        }
        const mod = documentSnapshot.get('mod')
        const reason = documentSnapshot.get('reason');
        const time = documentSnapshot.get('time');

        let type = documentSnapshot.get('type');
        if (type == 1){
          type = "Blacklist";
        } else if (type == 2){
          type = "Dayban";
        } else if (type == 3){
          type = "Warning";
        }

        const username = await API.getUsernameFromId(user);
        const modname = await API.getUsernameFromId(mod);

        const historyEmbed = new MessageEmbed()
          .setColor('#0099ff')
          .setTitle(`'Punishment of ${username}:${user}`)
          .setDescription(`This is a punishment log.`)
          .addFields(
            { name: 'Status', value: `${active}`},
            { name: 'Moderator', value: `${modname}:${mod}` },
            { name: 'Reason', value: `${reason}` },
            { name: 'Type', value: `${type}` },
            { name: 'Time', value: `<t:${time}>`}
          )

        historyArray.push(historyEmbed);

        if (historyArray.length >= length) {
          return historyArray;
        }
      }
    }
  });
}

问题原因 #

1. 函数未返回有效结果：CheckHistory是async函数，但内部调用colRef.get().then(...)时，没有把这个Promise返回出去。then回调里的return只是回调自身的返回值，不会成为外层函数的返回值，导致函数默认返回一个resolved为undefined的Promise。
2. 控制台打印对象错误：调用代码里console.log(CheckHistory)是直接打印函数本身，而非await后得到的结果hist，这才会出现[AsyncFunction: CheckHistory]的输出。
3. 隐性代码问题：
   • active = true是赋值操作，不是相等判断，应该写成active === true或者直接if (active)
   • length变量未声明，会污染全局作用域
   • 如果CheckBan(user)是异步函数，未加await会导致后续代码提前执行

解决方法 #

1. 修复调用代码 #

把打印对象改成hist，查看函数返回的实际结果：

let hist = await CheckHistory(id);
console.log(hist); // 打印函数返回的结果，而非函数本身

2. 重构CheckHistory函数 #

用await替代.then()，让异步逻辑更清晰，同时确保函数返回正确结果：

async function CheckHistory(user){
  // 如果CheckBan是异步函数，必须加await
  await CheckBan(user);
  let historyArray = [];

  const colRef = db.collection('punishments');
  const querySnapshot = await colRef.where('user', '==', user).get(); // 用await获取查询结果

  const length = querySnapshot.size; // 声明length变量，避免全局污染
  if (querySnapshot.empty){
    console.log(querySnapshot.size);
    return 0; // 无记录时返回0
  } else {
    let docs = querySnapshot.docs;
    for (let documentSnapshot of docs) {
      const revoke = documentSnapshot.get('revoke');

      // 修复判断逻辑，直接用布尔值判断
      let active = documentSnapshot.get('active') ? "Active" : `Revoked for ${revoke}`;

      const mod = documentSnapshot.get('mod');
      const reason = documentSnapshot.get('reason');
      const time = documentSnapshot.get('time');

      // 用switch替代多分支if，提升可读性
      let type = documentSnapshot.get('type');
      switch(type) {
        case 1: type = "Blacklist"; break;
        case 2: type = "Dayban"; break;
        case 3: type = "Warning"; break;
        default: type = "Unknown"; // 处理未知类型
      }

      const username = await API.getUsernameFromId(user);
      const modname = await API.getUsernameFromId(mod);

      const historyEmbed = new MessageEmbed()
        .setColor('#0099ff')
        .setTitle(`Punishment of ${username}:${user}`) // 去掉多余的单引号
        .setDescription(`This is a punishment log.`)
        .addFields(
          { name: 'Status', value: active },
          { name: 'Moderator', value: `${modname}:${mod}` },
          { name: 'Reason', value: reason },
          { name: 'Type', value: type },
          { name: 'Time', value: `<t:${time}>`}
        );

      historyArray.push(historyEmbed);
    }
    return historyArray; // 遍历完所有记录后返回数组
  }
}

关键修改说明 #

• 用await替代.then()，让异步逻辑线性化，确保函数能返回包含查询结果的Promise
• 修复active的判断错误，避免赋值操作替代判断逻辑
• 声明length变量，避免全局作用域污染
• 循环结束后直接返回数组，无需额外判断长度（循环会遍历所有文档）
• 修复标题中的多余单引号问题
• 用switch优化类型判断逻辑，提升代码可读性

内容的提问来源于stack exchange，提问作者Charley