Javascript 使用Node.js将值从承诺传递到承诺

我正在尝试传递一个我使用firebase一块一块地构建的对象。如果有更好的方法一步一步地构造对象，我并不需要沿着承诺链传递对象。这是我的密码：

    var queue = new Queue(productUpdateQueue, function(data, progress, resolve, reject) {

    var incomingUpdateData = data;
    var receiptID = incomingUpdateData.receiptID;
    var userID = incomingUpdateData.userID;
    var oldProductID = incomingUpdateData.oldProductID;
    var newProductID = incomingUpdateData.newProductID;
    var newReceipt = incomingUpdateData.newReceipt;

    var postID = "";

    var updateObject = {};

    updateObject['usersPrivate/'+userID+'/receipts/'+receiptID+'/items/'+oldProductID] = null;
    updateObject['usersPrivate/'+userID+'/receipts/'+receiptID+'/items/'+newProductID] = newReceipt;

    clicks.child('VigLink').orderByChild('item').equalTo(oldProductID).once('value', function(cuidSnapshot) {
        return cuidSnapshot.forEach(function(cuidSnapshot) {
            var cuid = cuidSnapshot.key;
            updateObject['clicks/VigLink/'+cuid+'/item'] = newProductID;
            console.log('one');
            progress(20);
        });
    }).then(function() {
        return userReceiptMetrics.child(userID).child('receipts').child(receiptID).child('items').child(oldProductID).once('value', function(oldSnapshot) {
            var data = oldSnapshot.val()
            updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/items/'+oldProductID] = null
            updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/items/'+newProductID] = data
            if (data != null) {
                updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/itemIDs/'+newProductID] = now
                updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/itemIDs/'+oldProductID] = null
            };
            console.log('two');
            progress(40);
        });
    }).then(function() {
        return userReceiptMetrics.child(userID).child('shops').child(oldProductID).once('value', function(oldSnapshot) {
            var data = oldSnapshot.val()
            updateObject['userReceiptMetrics/'+userID+'/shops/'+oldProductID] = null;
            updateObject['userReceiptMetrics/'+userID+'/shops/'+newProductID] = data;
            if (data != null) {
                updateObject['userReceiptMetrics/'+userID+'/shopIDs/'+newProductID] = now;
                updateObject['userReceiptMetrics/'+userID+'/shopIDs/'+oldProductID] = null;
            };
            console.log('three');
            progress(60);
        });
    }).then(function() {
        return posts.once('value', function(postSnapshot) {
            // use Promise.all and Array#map to wait for all these queries to finish

            var allPosts = postSnapshot.val()
            var postKeys = Object.keys(allPosts)

            return Promise.all(postKeys.map(function(postKey) {
                var postID = postKey;

                return posts.child(postID).child('items').child(oldProductID).once('value', function(itemSnapshot) {

                    itemSnapshot.forEach(function(itemSnapshot) {
                        var itemData = itemSnapshot.val()
                        console.log('post snapshot'+ itemSnapshot);
                        updateObject['posts/'+postID+'/items/'+oldProductID] = null
                        updateObject['posts/'+postID+'/items/'+newProductID] = itemData
                    });
                });
            })).then(function(results) {
                // put progress update in .then, and return the results 
                progress(75);
                return results;
            });
        });
    }).then(function() {
        // Move to next item
        return console.log('hey look here'+updateObject['posts/'+postID+'/items/'+newProductID]);
        return firebaseRoot.update(updateObject, function(error) {
            if (error) {
                console.log("Error updating data:", error);
                reject()
            } else {
                progress(100);
                // resolve();
                console.log('four');
            }
        });
    });

    // Finish the task asynchronously
    setTimeout(function() {
        reject();
    }, 10000);
});

输出为：

one
two
three
hey look hereundefined
post snapshot[object Object]
post snapshot[object Object]
post snapshot[object Object]
post snapshot[object Object]
post snapshot[object Object]
post snapshot[object Object]
post snapshot[object Object]
post snapshot[object Object]

---

非常感谢您的任何帮助。

您需要更改您的。然后从（现在问题中已更改，但代码最初有此功能）

到

因此，您的代码总是更新在

新队列

回调中声明的updateObject

此外，每行中的第一行需要添加一个返回

因此，与其

userReceiptMetrics.child(userID).child('receipts').child(receiptID).child('items').child(oldProductID).once('value', function(oldSnapshot) {

你有

return userReceiptMetrics.child(userID).child('receipts').child(receiptID).child('items').child(oldProductID).once('value', function(oldSnapshot) {

进度调用需要放在.once回调的末尾

总之，代码应该看起来像（删除了大部分正确的代码，希望这是可以理解的）

var queue = new Queue(productUpdateQueue, function(data, progress, resolve, reject) {
    // removed for brevity
    var updateObject = {};
    // removed for brevity
    clicks.child('VigLink').orderByChild('item').equalTo(oldProductID).once('value', function(cuidSnapshot) {
        // removed for brevity
        progress(12);
    }).then(function() {
        return userReceiptMetrics.child(userID).child('receipts').child(receiptID).child('items').child(oldProductID).once('value', function(oldSnapshot) {
            // removed for brevity
            progress(25);
        });
    }).then(function() {
        return userReceiptMetrics.child(userID).child('shops').child(oldProductID).once('value', function(oldSnapshot) {
            // removed for brevity
            progress(50);
        });
    }).then(function() {
        return posts.orderByChild('items').equalTo(oldProductID).once('value', function(postSnapshot) {
            // use Promise.all and Array#map to wait for all these queries to finish
            return Promise.all(postSnapshot.map(function(postSnapshot) {
                var postID = postSnapshot.key;

                return posts.child(postID).child('items').child(oldProductID).once('value', function(itemSnapshot) {

                    itemSnapshot.forEach(function(itemSnapshot) {
                        var itemData = itemSnapshot.val()

                        updateObject['posts/'+postID+'/items/'+oldProductID] = null
                        updateObject['posts/'+postID+'/items/'+newProductID] = itemData
                    });
                });
            })).then(function(results) {
                // put progress update in .then, and return the results 
                progress(75);
                return results;
            });
        });
    }).then(function() {
        // Move to next item
        console.log(updateObject);
        // removed for brevity
    });

    // Finish the task asynchronously
    setTimeout(function() {
        reject();
    }, 10000);
});

---

所以我终于想出了方法。我在一步一步地传递对象时遇到了一个问题，但我真正想做的是一步一步地创建对象。所以我在承诺链之外创建了对象，并一步一步地构建它。这里的主要障碍之一是完成循环，然后继续下一个promis为此，我使用

Promise.all（）

返回结果

它是有效的，现在我对承诺的作用有了更多的了解。如果这能帮助你，请接受：

var queue = new Queue(productUpdateQueue, function(data, progress, resolve, reject) {

    var incomingUpdateData = data;
    var receiptID = incomingUpdateData.receiptID;
    var userID = incomingUpdateData.userID;
    var oldProductID = incomingUpdateData.oldProductID;
    var newProductID = incomingUpdateData.newProductID;
    var newReceipt = incomingUpdateData.newReceipt;

    var postID = "-KZOO0UII67uOmYo6DJh";

    var postKeys = [];

    var updateObject = {};

    updateObject['usersPrivate/'+userID+'/receipts/'+receiptID+'/items/'+oldProductID] = null;
    updateObject['usersPrivate/'+userID+'/receipts/'+receiptID+'/items/'+newProductID] = newReceipt;

    return clicks.child('VigLink').orderByChild('item').equalTo(oldProductID).once('value', function(cuidSnapshot) {
        return cuidSnapshot.forEach(function(cuidSnapshot) {
            var cuid = cuidSnapshot.key;
            updateObject['clicks/VigLink/'+cuid+'/item'] = newProductID;
            progress(10);
        });
    }).then(function() {
        return userReceiptMetrics.child(userID).child('receipts').child(receiptID).child('items').child(oldProductID).once('value', function(oldSnapshot) {
            var data = oldSnapshot.val()
            updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/items/'+oldProductID] = null
            updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/items/'+newProductID] = data
            if (data != null) {
                updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/itemIDs/'+newProductID] = now
                updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/itemIDs/'+oldProductID] = null
            };
            progress(25);
        });
    }).then(function() {
        return userReceiptMetrics.child(userID).child('shops').child(oldProductID).once('value', function(oldSnapshot) {
            var data = oldSnapshot.val()
            updateObject['userReceiptMetrics/'+userID+'/shops/'+oldProductID] = null;
            updateObject['userReceiptMetrics/'+userID+'/shops/'+newProductID] = data;
            if (data != null) {
                updateObject['userReceiptMetrics/'+userID+'/shopIDs/'+newProductID] = now;
                updateObject['userReceiptMetrics/'+userID+'/shopIDs/'+oldProductID] = null;
            };
            progress(40);
        });
    }).then(function() {
        progress(55);
        return posts.orderByChild('receipt').equalTo(receiptID).once('value');
    }).then(function(postSnapshot) {
        return postSnapshot.forEach(function(post) {
            progress(70);
            postKeys.push(post.key)
        });
    }).then(function() {
        return Promise.all(postKeys.map(function(postKey) {
            return posts.child(postKey).child('items').child(oldProductID).once('value', function(itemSnapshot) {
                var itemData = itemSnapshot.val()
                updateObject['posts/'+postKey+'/items/'+oldProductID] = null;
                updateObject['posts/'+postKey+'/items/'+newProductID] = itemData;
            });
        })).then(function(results) {
            progress(85);
            return results;
        });
    }).then(function() {
        return firebaseRoot.update(updateObject, function(error) {
            if (error) {
                console.log("Error updating data:", error);
                reject()
            } else {
                progress(100);
                resolve();
            }
        });
    });

    // Finish the task asynchronously
    setTimeout(function() {
        reject();
    }, 10000);
});

---

您是否可以检查执行是否实际进入为userReceiptMetrics.child（userID）.child（'receipts'）.child（receiptID.）.child（'items'）.child（oldProductID）上的值事件注册的回调变量？正如我现在看到的，它永远不会退出第一个承诺部分。我看到进度设置为12，然后服务器崩溃。那么，是什么让你说它永远不会退出第一个承诺呢？报告的错误似乎指向试图影响updateObject['userReceiptMetrics/'+userID+'/shops/'+oldProductID]的指令是的，这是我没有得到的。如果我把console.log（）语句放在第一个承诺之外的任何地方，它就不会被调用。此外，我正在看着它在运行时（在崩溃之前）将数据放在我的firebase上而且它似乎只是在崩溃前将进度设置为12的部分。真的，我想可能

return updateObject；

不会将对象传递给下一个承诺，因此

updateObject

是未定义的。我错了吗？感谢十亿Jaromanda X！！我很确定他们的承诺是按顺序发生的在我将对象设置到Firebase之前，我做了一些其他错误。你的帮助非常有用，正因为如此，我在本周六授予你“g”奖。你是正式的g.Ok。因此，看起来除了一个问题外，这一切都正常。我使用的两个循环都在整个承诺链结束后完成。你不能使用吗承诺中的循环？抱歉，没有注意到forEach循环也使用异步代码-让我修改我编辑的答案（希望如此）对于在forEach内部使用asynch的部分，正确的代码-它使用Promise.all和Array#map来等待所有内部查询的解析它告诉我，

.map不是一个函数

var queue = new Queue(productUpdateQueue, function(data, progress, resolve, reject) {
    // removed for brevity
    var updateObject = {};
    // removed for brevity
    clicks.child('VigLink').orderByChild('item').equalTo(oldProductID).once('value', function(cuidSnapshot) {
        // removed for brevity
        progress(12);
    }).then(function() {
        return userReceiptMetrics.child(userID).child('receipts').child(receiptID).child('items').child(oldProductID).once('value', function(oldSnapshot) {
            // removed for brevity
            progress(25);
        });
    }).then(function() {
        return userReceiptMetrics.child(userID).child('shops').child(oldProductID).once('value', function(oldSnapshot) {
            // removed for brevity
            progress(50);
        });
    }).then(function() {
        return posts.orderByChild('items').equalTo(oldProductID).once('value', function(postSnapshot) {
            // use Promise.all and Array#map to wait for all these queries to finish
            return Promise.all(postSnapshot.map(function(postSnapshot) {
                var postID = postSnapshot.key;

                return posts.child(postID).child('items').child(oldProductID).once('value', function(itemSnapshot) {

                    itemSnapshot.forEach(function(itemSnapshot) {
                        var itemData = itemSnapshot.val()

                        updateObject['posts/'+postID+'/items/'+oldProductID] = null
                        updateObject['posts/'+postID+'/items/'+newProductID] = itemData
                    });
                });
            })).then(function(results) {
                // put progress update in .then, and return the results 
                progress(75);
                return results;
            });
        });
    }).then(function() {
        // Move to next item
        console.log(updateObject);
        // removed for brevity
    });

    // Finish the task asynchronously
    setTimeout(function() {
        reject();
    }, 10000);
});

var queue = new Queue(productUpdateQueue, function(data, progress, resolve, reject) {

    var incomingUpdateData = data;
    var receiptID = incomingUpdateData.receiptID;
    var userID = incomingUpdateData.userID;
    var oldProductID = incomingUpdateData.oldProductID;
    var newProductID = incomingUpdateData.newProductID;
    var newReceipt = incomingUpdateData.newReceipt;

    var postID = "-KZOO0UII67uOmYo6DJh";

    var postKeys = [];

    var updateObject = {};

    updateObject['usersPrivate/'+userID+'/receipts/'+receiptID+'/items/'+oldProductID] = null;
    updateObject['usersPrivate/'+userID+'/receipts/'+receiptID+'/items/'+newProductID] = newReceipt;

    return clicks.child('VigLink').orderByChild('item').equalTo(oldProductID).once('value', function(cuidSnapshot) {
        return cuidSnapshot.forEach(function(cuidSnapshot) {
            var cuid = cuidSnapshot.key;
            updateObject['clicks/VigLink/'+cuid+'/item'] = newProductID;
            progress(10);
        });
    }).then(function() {
        return userReceiptMetrics.child(userID).child('receipts').child(receiptID).child('items').child(oldProductID).once('value', function(oldSnapshot) {
            var data = oldSnapshot.val()
            updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/items/'+oldProductID] = null
            updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/items/'+newProductID] = data
            if (data != null) {
                updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/itemIDs/'+newProductID] = now
                updateObject['userReceiptMetrics/'+userID+'/receipts/'+receiptID+'/itemIDs/'+oldProductID] = null
            };
            progress(25);
        });
    }).then(function() {
        return userReceiptMetrics.child(userID).child('shops').child(oldProductID).once('value', function(oldSnapshot) {
            var data = oldSnapshot.val()
            updateObject['userReceiptMetrics/'+userID+'/shops/'+oldProductID] = null;
            updateObject['userReceiptMetrics/'+userID+'/shops/'+newProductID] = data;
            if (data != null) {
                updateObject['userReceiptMetrics/'+userID+'/shopIDs/'+newProductID] = now;
                updateObject['userReceiptMetrics/'+userID+'/shopIDs/'+oldProductID] = null;
            };
            progress(40);
        });
    }).then(function() {
        progress(55);
        return posts.orderByChild('receipt').equalTo(receiptID).once('value');
    }).then(function(postSnapshot) {
        return postSnapshot.forEach(function(post) {
            progress(70);
            postKeys.push(post.key)
        });
    }).then(function() {
        return Promise.all(postKeys.map(function(postKey) {
            return posts.child(postKey).child('items').child(oldProductID).once('value', function(itemSnapshot) {
                var itemData = itemSnapshot.val()
                updateObject['posts/'+postKey+'/items/'+oldProductID] = null;
                updateObject['posts/'+postKey+'/items/'+newProductID] = itemData;
            });
        })).then(function(results) {
            progress(85);
            return results;
        });
    }).then(function() {
        return firebaseRoot.update(updateObject, function(error) {
            if (error) {
                console.log("Error updating data:", error);
                reject()
            } else {
                progress(100);
                resolve();
            }
        });
    });

    // Finish the task asynchronously
    setTimeout(function() {
        reject();
    }, 10000);
});