Javascript 角度延迟实现仅输出循环的最后一个值

我有一个自定义的同步过程，在这个过程中，我按顺序将所有同步记录排队。当我的服务检索到多个同步记录时，它将处理这些记录，然后为每个成功记录更新我的上次同步日期，或者在失败时记录我的错误（不更新上次同步日期）并中止同步过程

我已经从AngularJS实现了$q.all。以下是同步循环的一个子集：

    var processes = [];

    for (var i in data) {
        if (data[i] === null || data[i].TableName == null || data[i].Query == null || data[i].Params == null) {
            // Let's throw an error here...
            throw new TypeError("ERROR! The data retrieved from the download sync process was of an unexpected type.");
        }

        var params = data[i].Params;
        var paramsMassaged = params.replaceAll("[", "").replaceAll("]", "").replaceAll(", ", ",").replaceAll("'", "");
        var paramsArray = paramsMassaged.split(",");

        mlog.Log("Query: " + data[i].Query);
        mlog.Log("Params: " + paramsArray);

        if (data[i].TableName === "table1") {
            var process = $table1_DBContext.ExecuteSyncItem(data[i].Query, paramsArray);

            process.then(
                function () {
                    $DBConfigurations_DBContext.UpdateLastSyncDate(data[i].CreatedDate, function (response) {
                        mlog.Log(response);
                    });
                },
                function (response) {
                    mlog.LogSync("Error syncing record: " + response, "ERROR", data[i].Id);
                },
                null
            );

            processes.push(process);
        } else if (data[i].TableName === "table2") {
            var process = $table2_DBContext.ExecuteSyncItem(data[i].Query, paramsArray);

            process.then(
                function () {
                    $DBConfigurations_DBContext.UpdateLastSyncDate(data[i].CreatedDate, function (response) {
                        mlog.Log(response);
                    });
                },
                function (response) {
                    mlog.LogSync("Error syncing record: " + response, "ERROR", data[i].Id);
                },
                null
            );

            processes.push(process);
        } else {
            mlog.LogSync("WARNING! This table is not included in the sync process. You have an outdated version of the application. Table: " + data[i].TableName);
        }
    }

    $q.all(processes)
        .then(function (result) {
            mlog.LogSync("---Finished syncing all records");
        }, function (response) {
            mlog.LogSync("Sync Failure - " + response, "ERROR");
        });

ExecuteSyncItem函数示例：

ExecuteSyncItem: function (script, params) {
    window.logger.logIt("In the table1 ExecuteSyncItem function...");

    var primaryKey = params[params.length - 1];

    var deferred = $q.defer();

    $DBService.ExecuteQuery(script, params,
        function (insertId, rowsAffected, rows) {
            window.logger.logIt("rowsAffected: " + rowsAffected.rowsAffected);

            if (rowsAffected.rowsAffected <= 1) {
                deferred.resolve();
            } else {
                deferred.resolve(errorMessage);
            }
        },
        function (tx, error) {
            deferred.reject("Failed to sync table1 record with primary key: " + primaryKey + "; Error: " + error.message);
        }
    );

    return deferred.promise;
}

---

如何让它显示失败的特定记录的信息，而不是显示相同的消息“x”次？

问题在于您在I上的关闭。执行回调函数时，i的值将是for循环中的最后一个值。您需要将该值i绑定到一个单独的、不变的值。最简单的方法是使用自调用函数

for (var i in data) {
    (function(item) {
        // Put your logic in here and use item instead of i, for example
        mlog.LogSync("Error syncing record: " + response, "ERROR", data[item].Id
    })(i);
}

下面是一篇关于闭包为什么会导致这种情况的好文章（这是一个非常常见的问题）：

---

正如

comradburk

所提到的，将进程封装在一个循环中是一个很好的解决方案，但是有一种

角度的方法来解决这个问题。您可以通过
angular.forEach（）
并循环所有
数据
元素，而不是使用本机
for in
循环

var processes = [];

angular.forEach(data, function(item) {
    if (item === null || item.TableName == null || item.Query == null || item.Params == null) {
        // Let's throw an error here...
        throw new TypeError("ERROR! The data retrieved from the download sync process was of an unexpected type.");
    }

    var params = item.Params;
    var paramsMassaged = params.replaceAll("[", "").replaceAll("]", "").replaceAll(", ", ",").replaceAll("'", "");
    var paramsArray = paramsMassaged.split(",");

    mlog.Log("Query: " + item.Query);
    mlog.Log("Params: " + paramsArray);

    if (item.TableName === "table1") {
        var process = $table1_DBContext.ExecuteSyncItem(item.Query, paramsArray);

        process.then(
            function () {
                $DBConfigurations_DBContext.UpdateLastSyncDate(item.CreatedDate, function (response) {
                    mlog.Log(response);
                });
            },
            function (response) {
                mlog.LogSync("Error syncing record: " + response, "ERROR", item.Id);
            },
            null
        );

        processes.push(process);
    } else if (item.TableName === "table2") {
        var process = $table2_DBContext.ExecuteSyncItem(item.Query, paramsArray);

        process.then(
            function () {
                $DBConfigurations_DBContext.UpdateLastSyncDate(item.CreatedDate, function (response) {
                    mlog.Log(response);
                });
            },
            function (response) {
                mlog.LogSync("Error syncing record: " + response, "ERROR", item.Id);
            },
            null
        );

        processes.push(process);
    } else {
        mlog.LogSync("WARNING! This table is not included in the sync process. You have an outdated version of the application. Table: " + item.TableName);
    }
});

$q.all(processes)
    .then(function (result) {
        mlog.LogSync("---Finished syncing all records");
    }, function (response) {
        mlog.LogSync("Sync Failure - " + response, "ERROR");
    });

我知道这超出了你问题的范围。但是您正在加倍编写$table1_DBContext&&$table2_DBContext的代码，惟一的区别是DB引用。为什么不配置它，然后引用它，这样您只需对该块编写一次代码？id..var config={'table1'：$table1\u DBContentext等..}然后在代码中：var process=config[data[i].TableName].ExecuteSyncItem。。当然，在你的“如果”中测试一下。詹姆斯马农你绝对是对的。我计划在不久的将来进行重构。
var processes = [];

angular.forEach(data, function(item) {
    if (item === null || item.TableName == null || item.Query == null || item.Params == null) {
        // Let's throw an error here...
        throw new TypeError("ERROR! The data retrieved from the download sync process was of an unexpected type.");
    }

    var params = item.Params;
    var paramsMassaged = params.replaceAll("[", "").replaceAll("]", "").replaceAll(", ", ",").replaceAll("'", "");
    var paramsArray = paramsMassaged.split(",");

    mlog.Log("Query: " + item.Query);
    mlog.Log("Params: " + paramsArray);

    if (item.TableName === "table1") {
        var process = $table1_DBContext.ExecuteSyncItem(item.Query, paramsArray);

        process.then(
            function () {
                $DBConfigurations_DBContext.UpdateLastSyncDate(item.CreatedDate, function (response) {
                    mlog.Log(response);
                });
            },
            function (response) {
                mlog.LogSync("Error syncing record: " + response, "ERROR", item.Id);
            },
            null
        );

        processes.push(process);
    } else if (item.TableName === "table2") {
        var process = $table2_DBContext.ExecuteSyncItem(item.Query, paramsArray);

        process.then(
            function () {
                $DBConfigurations_DBContext.UpdateLastSyncDate(item.CreatedDate, function (response) {
                    mlog.Log(response);
                });
            },
            function (response) {
                mlog.LogSync("Error syncing record: " + response, "ERROR", item.Id);
            },
            null
        );

        processes.push(process);
    } else {
        mlog.LogSync("WARNING! This table is not included in the sync process. You have an outdated version of the application. Table: " + item.TableName);
    }
});

$q.all(processes)
    .then(function (result) {
        mlog.LogSync("---Finished syncing all records");
    }, function (response) {
        mlog.LogSync("Sync Failure - " + response, "ERROR");
    });