JavaScript Revealing Module Pattern Variable Scope

Question

I have an issue where I can't get to a variable inside a function:

EDIT I forgot to add that I am setting this workerPage.grid = $("#grid").data("kendoGrid"); on the jQuery $(function(){});

I can't use claimsGird variable inside the save function, I have to referenec it by workerPage.grid. Not the other variables like viewModel work fine. Here is the snippet:

save = function () {
                saif.kendoGridUtils.addModifiedDataItems(
                    viewModel.CompanionClaims.Updated,
                    viewModel.CompanionClaims.Added,
                    $("#grid").data("kendoGrid").dataSource.data()
                );

                $.ajax({
                    url: $("#contentForm").attr("action"),
                    data: JSON.stringify(viewModel),
                    type: "POST",
                    contentType: "application/json"
                }).success(function (data) {
                    //syncs viewModel with changes in model
                    $.extend(viewModel, kendo.observable(data));

                    //rebinds the grid data source
                    claimsGrid.dataSource.data(viewModel.CompanionClaims.Rows);

Here is the full script:

var workerPage = (function () {
        var viewModel = kendo.observable(@Html.Raw(Json.Encode(Model))),
            claimsGrid = null,
            deleteFirm = function (firmModel) {
                firmModel.Name = "";
                firmModel.AttorneyName = "";
                firmModel.Address.Line1 = "";
                firmModel.Address.Line2 = "";
                firmModel.Address.City = "";
                firmModel.Address.State = "OR";
                firmModel.Address.ZipCode = "";
                firmModel.Address.PlusFourCode = "";
                firmModel.PhoneNumber = "";
                firmModel.FaxNumber = "";
                firmModel.ContactName = "";
            },
            bind = function () {
                kendo.bind($("#main-content"), viewModel);
            },
            save = function () {
                saif.kendoGridUtils.addModifiedDataItems(
                    viewModel.CompanionClaims.Updated,
                    viewModel.CompanionClaims.Added,
                    $("#grid").data("kendoGrid").dataSource.data()
                );

                $.ajax({
                    url: $("#contentForm").attr("action"),
                    data: JSON.stringify(viewModel),
                    type: "POST",
                    contentType: "application/json"
                }).success(function (data) {
                    //syncs viewModel with changes in model
                    $.extend(viewModel, kendo.observable(data));

                    //rebinds the grid data source
                    claimsGrid.dataSource.data(viewModel.CompanionClaims.Rows);


                    //rebinds view elements to view model so changes are visible
                    //kendo.bind($("#main-content"), viewModel);
                    bind();

                    // Errors and Warnings
                    var results = messageUtils.parseMessages(
                        viewModel.Messages.Errors,
                        viewModel.Messages.Informationals,
                        viewModel.Messages.Warnings
                    );

                    var errs = $("#errors").html(results.errorMessages);
                    $("#informationals").html(results.informationalMessages);
                    $("#warnings").html(results.warningMessages);

                    $.each(saif.kendoGridUtils.processErrors(viewModel.CompanionClaims.Rows), function (i, message) {
                        errs.html(errs.html() + message + "<br>");
                    });
                    // End Errors and Warnings

                });
            },
            deleteRow = function () {
                var row = claimsGrid.select(),
                    rowDataItem = claimsGrid.dataItem(row),
                    rowIndex = $(row).index(),
                    addedItemIndex = $.inArray(rowDataItem, viewModel.CompanionClaims.Added);

                //add to Deleted if not new
                if (addedItemIndex == -1 && $.inArray(rowDataItem, viewModel.CompanionClaims.Rows) != -1) {
                    viewModel.CompanionClaims.Deleted.push(rowDataItem);
                }

                //remove from Added if exists
                if (addedItemIndex != -1) {
                    viewModel.CompanionClaims.Added.splice(addedItemIndex, 1);
                }

                claimsGrid.removeRow(row);

                //select the next row, eg. if you delete row 2, select the row that took that rows poisition after it was deleted.
                claimsGrid.select(claimsGrid.tbody.find(">tr:eq(" + rowIndex + ")"));
            };

        return {
            bind: bind,
            deleteFirm: deleteFirm,
            deleteRow: deleteRow,
            grid: claimsGrid,
            save: save,
            viewModel: viewModel
        };

    }());

The only assignment to the claimsGrid variable is claimsGrid = null. Have you missed to show some of the code? — nekman
– nekman, Commented Jan 23, 2013 at 19:47

Jonathan Lonowski · Accepted Answer · 2013-01-23 20:05:31Z

2

The issue is that claimsGrid is never set to anything other than null. And setting workerPage.grid won't change the value of claimsGrid -- it's not a pointer, just a copy.

You'll instead have to use a getter/setter. With newer browsers/engines, that can be done with get and set:

// ...
return {
    // ...
    get grid() {
        return claimsGrid;
    },
    set grid(grid) {
        claimsGrid = grid;
    },
    // ...
};

You can also define grid as a function:

// ...
function getOrSetGrid(grid) {
    if (typeof newGrid === 'undefined') {
        return claimsGrid;
    } else {
        claimsGrid = grid;
    }
}

return {
    // ...,
    grid: getOrSetGrid,
    // ...
};
// ...

// rather than: workerPage.grid = ...;
workerPage.grid(...);

Or split it into getGrid and setGrid functions.

edited Jan 23, 2013 at 20:05

answered Jan 23, 2013 at 19:48

Jonathan Lonowski

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4 Comments

Sam Over a year ago

I forgot to add that I am setting this workerPage.grid = $("#grid").data("kendoGrid"); on the jQuery $(function(){});

Jonathan Lonowski Over a year ago

@SamStriano Since you were including claimsGrid in the "reveal," I assumed that was the case. But, as I noted, setting workerPage.grid won't affect claimsGrid -- "it's not a pointer, just a copy."

Sam Over a year ago

Could you elaborate on "it's not a pointer, just a copy"? Maybe a link somewhere that explains this a little better? Thanks!!

Jonathan Lonowski Over a year ago

@SamStriano workerPage.grid doesn't have any ties back to claimsGrid beyond being the source of its initial value (the copy). It doesn't hold a reference to claimsGrid in any way (as a pointer would). They are instead entirely separate variables that just so happen to have the same value for a time. But, setting one to a new value won't be reflected in the other since they are separate.

groksrc · Accepted Answer · 2013-01-23 19:48:10Z

0

Scope in javascript works differently than other languages like Java or C#. In your case claimsGrid is not in scope for the save function. Does this help? http://coding.smashingmagazine.com/2009/08/01/what-you-need-to-know-about-javascript-scope/

answered Jan 23, 2013 at 19:48

groksrc

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