For循环不从猫鼬回调中更新数组

Question

我认为我的问题在于 JS 的异步特性。我正在尝试将项目推送到数组中，但它似乎没有更新它......我在 for 循环中做了 console.log 语句，并看到它用数字填充数组，但是当我 console.log循环外的数组，我得到一个空数组。我正在使用猫鼬。 有什么建议吗？

代码如下：

let collections = [];
                return Promise.all(courts.map(court => {
                  return new Promise((resolve, reject) => {
                    return Promise.all(court.users.map(async user => {
                      let tempPromise = new Promise((resolve, reject) => { 
                          setTimeout(() => {
                              resolve();
                          }, 5000);
                      });
                                  return SignDetail.find({
                                    userName: user.userName,
                                    signStatus: "signIn",
                                  }).then(function(sign) { 
                                    if (user.userName.endsWith('zs')) { 
                                        let signCount = 0;
                                        if (sign.length > 1) {
                                            for (let j = 0; j < sign.length; j++) {
                                                let courtObj = {courtName: sign[j].userName}; //make court object
                                                signCount++; //increment each time there's a signature
                                                if (j === sign.length - 1) { //only push object in array when all signatures have been counted
                                                    courtObj.signCount = signCount;
                                                    collections.push(courtObj);
                                                    console.log(collections)
                                                } 
                                            }
                                        } 

                                    } //end here
                                  }); 
                      return tempPromise;
                    })).then(_ => resolve(collections));
                  })
                })).then(collections => {
                  // HERE you will your collection and you can use this promise where this function is being called. 
                  console.log(collections);
                });

Answer 1

函数SignDetail.find()是异步函数，不能同步返回res.render。您需要从此函数返回一个承诺，该承诺将解析为所需的输出。

你可以这样做。

let collections = [];
return Promise.all(courts.map(court => {
  return new Promise((resolve, reject) => {
    return Promise.all(court.users.map(oUser => {
      var tempPromise = new Promise();
      if(oUser.userName.endsWith('zs')){
        SignDetail.find(
          {username: oUser.username. signStatus: 'signIn'}, 
          function(err, sign){
            collection.push(sign.length);
            tempPromise.resolve();
          })
      } else{
         tempPromise.resolve();
      }
      return tempPromise;
    })).then(_ => resolve());
  })
})).then(_ => {
  // HERE you will your collection and you can use this promise where this function is being called. 
  console.log(collections);
});