Jquery When and Deferred object, broken function flow

Question

I am using $.when and .done to make sure that the close window happens after the data is saved. But, this doesn't seem to work as expected.

The workflow is that, user clicks on a button "Save and Close", which should save the data first, trigger print and close the window. But the save data and close window happens at the same time which makes the print fail.

I have read about when..then and deferred object. Tried to implement it here the following code, sometimes it work but most of the time it would break.

$("#btnSaveAndClose").click(function (event) {
    $.when(zSaveSomeData()).done(function (value) {
        zCloseMyWindow();
    });
});

function zSaveSomeData() {
    return zSaveMasterData(masterdata, function () {  
        return zSaveDetailData();
    });
};

function zSaveMasterData(masterdata, fnAfterSave) {
    return $.ajax({
        type: 'POST',
        contentType: 'application/json',
        url: '/api/masterdata/',
        data: JSON.stringify(masterdata),
        success: function (data) {
            fnAfterSave();
        }
    });
};

function zSaveDetailData() {
    var selectedDataGroups;
    // some logic here

    zSaveDetails(selectedDataGroups);

};

function zSaveDetails(selectedDataGroups) {
    var deferred = $.Deferred();
    $.ajax({
        type: 'POST',
        contentType: 'application/json',
        url: '/api/detaildata/',
        data: JSON.stringify(selectedDataGroups),
        success: function (data) {
            var printableGroupIDs = [];
            $.each(data, function () {
                if (this.IsPrintable)
                    printableGroupIDs.push(this.ID);
            });

            if (printableGroupIDs.length > 0) {
                zPrintGroups(printableGroupIDs);
            }
            deferred.resolve('done');
        }
    });

    zAuditSave();
    return deferred.promise();
};

function zPrintGroups(newGroupIDs) {
    // calls external program to print groups

};

function zCloseWindow() {
    window.close();
};

function zAuditSave() {
    $.ajax({
        type: 'POST',
        contentType: 'application/json',
        url: '/api/audit'
        success: function (data) {

        }
    });
};

Only thing is that the save calls other methods inside to same master and details data. There are couple of ajax calls too. An unusual thing is that after the data is saved, there is a call to VB code that actually triggers a Print. I am so confused on why would close window fire before the other methods are executed. Any help would be appreciated.

Answer 1

For me the code is overly divided into functions, with some doing little more than fronting for others.

I would prefer to see the click handler as a comprehensive master routine which sequences three promise-returning functions zSaveMasterData(), zSaveDetails() and zAuditSave(), then closes the window. Thus, some of the current functions will be subsumed by the click handler.

$("#btnSaveAndClose").click(function(event) {
    zSaveMasterData(masterdata).then(function() {
        var selectedDataGroups;
        /* some logic here */
        var detailsSaved = zSaveDetails(selectedDataGroups).then(function(data) {
            var printableGroupIDs = $.map(data, function (obj) {
                return obj.IsPrintable ? obj.ID : null;
            });
            if (printableGroupIDs.length > 0) {
                // calls external program to print groups
            }
        });
        // Here, it is assumed that zSaveDetails() and zAuditSave() can be performed in parallel.
        // If the calls need to be sequential, then the code will be slightly different.            
        return $.when(detailsSaved, zAuditSave());
    }).then(function() {
        window.close();
    });
});

function zSaveMasterData(masterdata) {
    return $.ajax({
        type: 'POST',
        url: '/api/masterdata/',
        contentType: 'application/json',
        data: JSON.stringify(masterdata),
    });
};

function zSaveDetails(selectedDataGroups) {
    return $.ajax({
        type: 'POST',
        contentType: 'application/json',
        url: '/api/detaildata/',
        data: JSON.stringify(selectedDataGroups)
    });
};

function zAuditSave() {
    return $.ajax({
        type: 'POST',
        contentType: 'application/json',
        url: '/api/audit'
    });
};

Note the returns in the three functions with ajax calls. These returns are vital to the sequencing process.

A potentially bigger issue, not addressed in the question (nor in this answer) is how to recover from errors. Presumably, the database will be inconsistent if the sequence of saves was to fail part way through. It may well be better to ditch this client-side sequencing approach in favour of a server-side transaction that the client sees as a single operation.

Answer 2

It seems like your problem is that you are doing asynchronous things inside an ajax success callback. The promise returned by $.ajax still resolves immediately after the response is received - and executes your done callback before the asynchronous zSaveDetailData() has finished.

So, to chain asynchronous actions, always use then. Use it even for synchronous actions, it makes the sequence clear.

Don't use success callbacks when you're working with promises. You also don't need deferreds. You might want to have a look at these generic rules as well, especially that you never must forget to return promises from async functions that you want to await.

$("#btnSaveAndClose").click(function (event) {
    zSaveSomeData().then(zCloseMyWindow);
});

function zSaveSomeData() {
    return zSaveMasterData(masterdata).then(zSaveDetailData);
}

function zSaveMasterData(masterdata) {
    return $.ajax({
        type: 'POST',
        contentType: 'application/json',
        url: '/api/masterdata/',
        data: JSON.stringify(masterdata),
    });
}

function zSaveDetailData() {
    var selectedDataGroups;
    // some logic here

    return zSaveDetails(selectedDataGroups);
//  ^^^^^^
}

function zSaveOrderGroups(selectedDataGroups) {
    return $.ajax({
//  ^^^^^^
        type: 'POST',
        contentType: 'application/json',
        url: '/api/detaildata/',
        data: JSON.stringify(selectedDataGroups)
    }).then(function(data) {
//    ^^^^^^^^^^^^^^^^^^^^^^
        var printableGroupIDs = [];
        $.each(data, function () {
            if (this.IsPrintable)
                 printableGroupIDs.push(this.ID);
        });
        if (printableGroupIDs.length > 0) {
            return zPrintGroups(printableGroupIDs);
//          ^^^^^^
        }
    }).then(zAuditSave);
//    ^^^^^^^^^^^^^^^^^
}

function zPrintGroups(newGroupIDs) {
    // calls external program to print groups
}

function zCloseWindow() {
    window.close();
}

function zAuditSave() {
    return $.ajax({
//  ^^^^^^
        type: 'POST',
        contentType: 'application/json',
        url: '/api/audit'
    });
}

Answer 3

The problem here is your code doesn't depend on when fnAfterSave() has completed.

Short answer: don't mix success methods, callbacks, and promises - use one pattern and stick to it - and the easiest pattern to use is promises.

$("#btnSaveAndClose").click(function (event) {
    zSaveSomeData().then(function() { zCloseMyWindow(); });
});

function zSaveSomeData() {
    return zSaveMasterData(masterdata).then(function(data) { zSaveDetailData() });
};

function zSaveMasterData(masterdata) {
    return $.ajax({
        type: 'POST',
        contentType: 'application/json',
        url: '/api/masterdata/',
        data: JSON.stringify(masterdata)
    });

    //remove success callback here as it breaks the chaining
};