#

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# DataTable

The DataTable widget is responsible for rendering columnar data into a highly customizable and fully accessible HTML table. The core functionality of DataTable is to visualize structured data as a table. A variety of class extensions can then be used to add features to the table such as sorting and scrolling.

## Getting Started

To include the source files for DataTable and its dependencies, first load the YUI seed file if you haven't already loaded it.

    <script src="http://yui.yahooapis.com/3.10.3/build/yui/yui-min.js"></script>

Next, create a new YUI instance for your application and populate it with the modules you need by specifying them as arguments to the `YUI().use()` method. YUI will automatically load any dependencies required by the modules you specify.

    <script>
    // Create a new YUI instance and populate it with the required modules.
    YUI().use('datatable', function (Y) {
        // DataTable is available and ready for use. Add implementation
        // code here.
    });
    </script>

For more information on creating YUI instances and on the `use()` method, see the documentation for the YUI Global Object.

Note: be sure to add the `yui3-skin-sam` classname to the page's `<body>` element or to a parent element of the widget in order to apply the default CSS skin. See Understanding Skinning.

## Upgrading from version 3.4.1 or older?

DataTable was refactored for 3.5.0. Some APIs were changed in backward incompatible ways.

Read the 3.5.0 Migration Guide for tips to avoid unpleasant surprises. If you still run into issues, please file a ticket.

If you are unable to upgrade due to unresolvable issues, you can use the `datatable-deprecated` module suite, which is equivalent to the 3.4.1 implementation. But be aware that these modules will be removed in a future version of YUI.

## DataTable Basics

A basic DataTable is made of columns and rows. Define the columns you want to display in your DataTable with the `columns` attribute. Rows are created for you based on the data you provide to the `data` attribute.

Under the hood, the DataTable class uses a ModelList instance to manage the row data properties. Read the Table Data Configuration section below for details about how to load, configure, and work with the table data.

    // Columns must match data object property names
    var data = [
        { id: "ga-3475", name: "gadget",   price: "$6.99", cost: "$5.99" },
        { id: "sp-9980", name: "sprocket", price: "$3.75", cost: "$3.25" },
        { id: "wi-0650", name: "widget",   price: "$4.25", cost: "$3.75" }
    ];

    var table = new Y.DataTable({
        columns: ["id", "name", "price"],
        data: data,

        // Optionally configure your table with a caption
        caption: "My first DataTable!",

        // and/or a summary (table attribute)
        summary: "Example DataTable showing basic instantiation configuration"
    });

    table.render("#example");

This code produces this table:

## Column Configuration

The `columns` attribute takes an array of field names that correspond to property names in the `data` objects. These field names are called "keys". As long as these keys exist in your data, DataTable will display the values in the table. By default, the key is also used as the label of the column header.

Use objects instead of key strings to customize how the cells in a column display.

    // Columns must match data object property names
    var data = [
        { id: "ga-3475", name: "gadget",   price: "$6.99", cost: "$5.99" },
        { id: "sp-9980", name: "sprocket", price: "$3.75", cost: "$3.25" },
        { id: "wi-0650", name: "widget",   /* missing */   cost: "$3.75" }
    ];

    var table = new Y.DataTable({
        columns: [
            "id",
            { key: "name", label: "part name" },
            { key: "price", allowHTML: true, emptyCellValue: "<em>(not set)</em>" },
            "cost"
        ],
        data: data
    });

    table.render("#example");

This code produces this table:

Some column configurations affect the table headers and others affect the data cells.

Use the `key` property to reference the associated data field when configuring columns with objects. Other supported configuration properties are listed in Appendix A below.

### Stacked Column Headers

Use the `children` column configuration to create multiple rows of column headers.

    var columns = [
        'username',
        {
            // Important: Parent columns do NOT get a key...

            // but DO get a label
            label: "Access",

            // Pass an array of column configurations (strings or objects) as children
            children: [
                'read',
                'write',
            ]
        }
    ];

    var data = [
        { username: "root", read: true, write: true },
        { username: "spilgrim", read: true, write: false },
        { username: "fizzgig", read: false, write: false }
    ];

    var table = new Y.DataTable({
        columns: columns,
        data   : data
    }).render("#example");

This code produces this table:

`children` takes an array of column configurations, just like the `columns` attribute itself. The columns defined in the `children` property will have header cells rendered below the parent column's header.

Columns that have `children` don't relate directly to the data cells in the table rows, so they should not have a `key` configured. They should, however, include a `label` to provide the header's content.

### Formatting Cell Data

Customizing the content of the cells in your table is done using column configurations. The most common formatting-related column configurations are:

- `allowHTML` - set this to `true` if your cell data, `emptyCellValue`, or `formatter` outputs HTML. By default, cell data is HTML escaped for security.
- `emptyCellValue` - string to populate cells where no data (empty string, `undefined`, or `null`) is available in a record.
- `formatter` - string or function used to translate the raw record data for each cell in a given column into a format better suited to display.
- `nodeFormatter` - function used to customize the DOM structure of a cell, its row, or its surrounding elements. Use with caution.

When the `formatter` configuration setting contains a string it will be assumed to be the key into the hash of formatting functions at `Y.DataTable.BodyView.Formatters`. If any such function is found, it will be used, otherwise, the string will be presumed to be a template which may contain placeholders for data enclosed in curly braces. The `{value}` placeholder would use the value destined for the current cell. The values of other fields in the record corresponding to the current row can be shown by providing their name enclosed in curly braces. These other fields don't need to have column definitions of their own, they will simply be read from the underlying Model instance.

The `Y.DataTable.BodyView.Formatters` is empty for the developers to provide their own formatting functions. A basic set is provided in module `datatable-formatters` that has to be explicitly loaded. Some of these named formatters accept extra configuration settings in the column definition, as described in their API docs.

`formatter` functions are expected to return the string content to populate each cell in that column, and `nodeFormatter`s are provided with the cell Nodes and expected to populate them using the Node API.

For best performance, avoid `nodeFormatter`s unless absolutely necessary.

    var columns = [
        {
            key: 'item',
            formatter: '<a href="#{value}">{value}</a>',
            allowHTML: true // Must be set or the html will be escaped
        },
        {
            key: 'cost',
            formatter: '${value}' // formatter template string
        },
        {
            key: 'price',
            formatter: function (o) {
                if (o.value > 3) {
                    o.className += 'expensive';
                }

                return '$' + o.value.toFixed(2);
            }
        },
        {
            label: 'profit',
            nodeFormatter: function (o) {
                var profit = o.data.price - o.data.cost,
                    prefix = '$',
                    row;

                if (profit < 0) {
                    prefix = '-' + prefix;
                    profit = Math.abs(profit);
                    row = o.cell.ancestor();

                    o.cell.addClass('negative');

                    // Assign a rowspan to the first cell and add a new row
                    // below this one to span the last three columns
                    row.one('td').setAttribute('rowspan', 2);

                    row.insert(
                        '<tr class="auth"><td colspan="3">' +
                            '<button class="ok">authorize</button>' +
                            '<button class="stop">discontinue</button>' +
                        '</td></tr>',
                        'after');
                }

                o.cell.set('text', prefix + profit.toFixed(2));
            }
        }
    ];

This code produces this table:

The parameters passed to `formatter` functions and `nodeFormatter` functions are described in Appendix B and Appendix C, respectively. Also look for what can be passed in to the columns in Appendix A.

Note: It's highly recommended to keep the data in the underlying `data` ModelList as pure data, free from presentational concerns. For example, use real numbers, not numeric strings, and store link urls and labels either in separate data fields or in a single data field, but as separate properties of a value object. This allows the data to be used for calculations such as sorting or averaging.

#### Setting content with `formatter` functions

Set the cell content with column `formatter`s by returning the desired content string from the function. Alternately, just update `o.value` with the new value in the object passed as an argument to the `formatter`. When updating `o.value` do not include a return statement.

`formatters` are very powerful because not only do they have access to the record's value for that column's field, but they also receive the rest of the record's data, the record Model instance itself, and the column configuration object. This allows you to include any extra configurations in your column configuration that might be useful to customizing how cells in the column are rendered.

    function currency(o) {
        return Y.DataType.Number.format(o.value, {
            prefix            : o.column.currencySymbol     || '$',
            decimalPlaces     : o.column.decimalPlaces      || 2,
            decimalSeparator  : o.column.decimalSeparator   || '.',
            thousandsSeparator: o.column.thousandsSeparator || ','
        });
    }

    var cols = [
        { key: "price", formatter: currency, decimalPlaces: 3 },
        ...

If such a formatter will be used regularly, it is best to store it in the `Y.DataTable.BodyView.Formatters` hash. The formatter can later be used by its name.

Named formatters are structured slightly differently in order to improve performance:

    Y.DataTable.BodyView.Formatters.currency = function (col) {
        // This is done just once per rendering cycle:
        var fn = Y.DataType.Number.format,
            format = {
                prefix            : col.currencySymbol     || '$',
                decimalPlaces     : col.decimalPlaces      || 2,
                decimalSeparator  : col.decimalSeparator   || '.',
                thousandsSeparator: col.thousandsSeparator || ','
            };
        return function (o) {
            // This is done once per row:
            return fn(o.value, format);
        }
    }

The function stored in the `Formatters` table is not the formatter function itself, instead, it returns the formatting function. The outer function is called just once per rendering cycle and does any preliminary setup usually based on the column configuration which it receives as its only argument, storing any information in local variables. The returned formatting function is then run once per row accessing all the setup information via closure.

An optional `datatable-formatters` module provides a collection of such formatters. See the API docs for more information on them.

See Appendix B for a list of all properties passed to `formatter` functions.

#### Setting content with `nodeFormatter` functions

Unlike `formatters` which can effectively default to the normal rendering logic by leaving `o.value` unchanged, `nodeFormatters` must assign content to the cells themselves. The cell's initial classes will be set up, but that's it. Everything else is your responsibility.

`nodeFormatter`s should return `false`. See below for details.

While there are few scenarios that require `nodeFormatter`s, they do have the benefits of having the Node API for constructing more complex DOM subtrees and the ability to access all nodes in the `<tbody>`. This means they can reference, and even modify, cells in other rows.

Like `formatters`, `nodeFormatters` are provided with the data field value, the record data, the record Model instance, and the column configuration object.

See Appendix C for a list of all properties passed to `nodeFormatter` functions.

#### Why `formatter` and `nodeFormatter`?

For good rendering performance and memory management, DataTable creates table content by assembling `innerHTML` strings from templates, with `{placeholder}` tokens replaced with your data. However, this means that the Nodes don't exist yet when a column's `formatter`s are applied.

To minimize the need to create Nodes for each cell, the default rendering logic supports the addition of cell classes as well as row classes via `formatter` functions. Event subscriptions should be delegated from the DataTable instance itself using the `delegate()` method.

On the rare occasion that you must use Nodes to supply the cell data, DataTable allows a second pass over the generated DOM elements once the initial string concatenation has been completed and the full HTML content created.

It is important to note that `nodeFormatters` will necessarily create a Node instance for each cell in that column, which will increase the memory footprint of your application. If the Node instance wrappers around the DOM elements don't need to be maintained beyond the life of the `nodeFormatter`, return `false` to remove them from the internal object cache. This will not remove the rendered DOM, but it will remove event subscriptions made on those Nodes.

In general, `nodeFormatter`s should only be used if absolutely necessary, and should always return `false`.

#### Formatters vs. `emptyCellValue`

The `emptyCellValue` configuration is useful to provide fallback content in the case of missing or empty column data, but it interacts with each type of formatter differently.

String formatters will only be applied if the field data for that cell is not `undefined`. This allows the `emptyCellValue` to populate the cell.

Function formatters are applied before the return value or (potentially altered) `o.value` property is tested for `undefined`, `null`, or the empty string. In any of these cases, the `emptyCellValue` populates the cell.

The `emptyCellValue` configuration is ignored by columns configured with `nodeFormatter`s.

## Table Data Configuration

Each record in the table is stored as a Model instance, where the keys of the record objects become Model attributes. This allows you to interact with the models as you would any other Base-based class, with `get(attr)`, `set(attr, value)`, and subscribing to attribute change events.

    var data = [
        { item: "widget",   cost: 23.57, price: 47.5 },
        { item: "gadget",   cost: 0.11, price: 6.99 },
        { item: "sprocket", cost: 4.08, price: 3.75 },
        { item: "nut",      cost: 0.01, price: 0.25 }
    ];

    var table = new Y.DataTable({
        columns: ["item", "cost", "price"],
        data: data
    });

    var sprocket = table.getRecord(2);

    // Fires a costChange event, and the table is updated if rendered
    sprocket.set('cost', 2.65);

The Model class used to store the record data is created for you, based on the objects in the `data` array. If `data` is not set, the column keys identified in the `columns` configuration is used.

### Specifying the Record Model

To use a custom Model for your records, pass your Model subclass to the `recordType` attribute.

    var pieTable = new Y.DataTable({
        recordType: Y.PieModel,
        columns: ['slices', 'type'],
        data: [
            // Y.PieModel has attributes 'slices', which defaults to 6, and 'type',
            // which defaults to 'apple'. Records can use these defaults.
            { type: 'lemon meringue' },
            { type: 'chocolate creme', slices: 8 },
            {} // equivalent to { type: 'apple', slices: 6 }
        ]
    });

    // Y.PieModel has its idAttribute assigned to 'type', overriding the default
    // of 'id'.  Fetch a PieModel by its id.
    var applePie = pieTable.getRecord('apple');

    // eatSlice is a method on the Y.PieModel prototype
    applePie.eatSlice();

Alternately, `recordType` will accept an array of attribute strings or an `ATTRS` configuration object to make it easier to create custom attribute behaviors without needing to explicitly build the Model subclass.

If the `columns` configuration is omitted, but the `recordType` is set, the `columns` will default to the `recordType`'s attributes.

    var data = [
        { item: "widget",   cost: 23.57, price: 47.5 },
        { item: "gadget",   cost: 0.11, price: 6.99 },
        { item: "sprocket", cost: 4.08, price: 3.75 },
        { item: "nut",      cost: 0.01, price: 0.25 }
    ];

    // Effectively synonymous with setting the columns attribute if no special
    // column configuration is needed.
    var table = new Y.DataTable({
        recordType: [ 'item', 'cost', 'price' ],
        data: data
    });

    // Or for more control, pass an ATTRS configuration object
    var table = new Y.DataTable({
        recordType: {
            item: {},
            cost: {
                value: 0,
                setter: function (val) { return +val || 0; }
            },
            price: {
                valueFn: function () { return (this.get('cost') + 0.1) * 10; },
                setter: function (val) { return +val || 0; }
            }
        },
        data: data
    });

When the table data is loaded asychronously, it is often a good idea to configure the `recordType`. This can prevent the generation of a record Model that is missing fields that are omitted from the `columns` configuration because they aren't intended for viewing.

### The `data` ModelList

The record Models are stored in a ModelList, which is assigned to the `data` property on the instance (for easier access than going through `table.get('data')`).

    var records = [
        { item: "widget",   cost: 23.57, price: 47.5 },
        { item: "gadget",   cost: 0.11, price: 6.99 },
        { item: "sprocket", cost: 4.08, price: 3.75 }
    ];

    var table = new Y.DataTable({
        columns: ["item", "cost", "price"],
        data   : records
    });

    // Add a new Model using the ModelList API. This will fire
    // events and change the table if rendered.
    table.data.add({ item: "nut", cost: 0.01, price: 0.25 });

When assigning the DataTable's `data` attribute with an array, a ModelList is created for you. But you can also pass a ModelList instance if you are sharing a ModelList between widgets on the page, or you have created custom Model and ModelList classes with additional logic, such as adding a data sync layer.

    var table = new Y.DataTable({
        columns: ['type', 'slices'],
        data: new Y.PieList()
    });

    // The Y.PieList class implements a sync layer, enabling its load() method
    table.data.load(function () {
        table.render('#pies');
    });

### Getting Remote Table Data

To fetch remote data, you have three options:

1. For quick one-offs, you can load and parse the data manually, using `Y.io(...)`, `Y.jsonp(...)`, etc., then assign that data to the DataTable's `data` attribute. This isn't very elegant or maintainable, so is best avoided for anything other than proofs of concept.

2. For the most control, better maintainability, and better encapsulation of business logic, create Model and ModelList subclasses that implement a sync layer as suggested above.

3. For common read-only scenarios, use the `Y.Plugin.DataTableDataSource` plugin to bind your table to a `DataSource` instance. Use plugins to add DataSource features.

    // Create a JSONP DataSource to query YQL
    var myDataSource = new Y.DataSource.Get({
        source: 'http://query.yahooapis.com/v1/public/yql?format=json&' +
                'env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&q='
    });

    myDataSource.plug(Y.Plugin.DataSourceJSONSchema, {
            schema: {
                resultListLocator: 'query.results.Result',
                resultFields: [
                    'Title',
                    'Phone',
                    {
                        // Important that record fields NOT include ".", so
                        // extract nested data with locators
                        key: 'Rating',
                        locator: "Rating.AverageRating"
                    }
                ]
            }
        })
        .plug(Y.Plugin.DataSourceCache, {
            max: 3
        });

    // No data is provided at construction because it will load via the
    // DataTableDataSource plugin
    var table = new Y.DataTable({
        columns: ['Title', 'Phone', 'Rating'],
        summary: 'Pizza places near 98089'
    });

    table.plug(Y.Plugin.DataTableDataSource, {
        datasource: myDataSource
    })

    // Initially render an empty table and show a loading message
    table.render('#pizza')
         .showMessage('loadingMessage');

    // Load the data into the table
    table.datasource.load({
        request: encodeURIComponent(
            'select *' +
            ' from   local.search' +
            ' where  zip="94089"' +
            ' and    query="pizza"');
    });

## DataTable Modules and Features

For a basic, stripped down `Y.DataTable` class, include the `datatable-base` module in your `use()`.

Feature modules, such as `datatable-sort`, will bring in `datatable-base` automatically. By including only feature modules in your `use()`, you will get a `Y.DataTable` that supports specifically those features, without extra code for other features you won't be using.

The `datatable` module is a bundle of `datatable-base` plus a set of common feature modules. Other feature modules need to be included explicitly in `use()`.

Module | Description | In `datatable`?
--- | --- | ---
`datatable-core` | The core API for DataTable, implemented as a class extension, used by `datatable-base` to create `Y.DataTable` and `Y.DataTable.Base`. | yes
`datatable-base` | Creates the `Y.DataTable` and `Y.DataTable.Base` classes, and defaults the `headerView` and `bodyView` to `Y.DataTable.HeaderView` and `Y.DataTable.BodyView` respectively. | yes
`datatable-head` | Creates the `Y.DataTable.HeaderView` class as a subclass of `Y.View`. DataTable defers rendering of the `<thead>` content to this View when it is passed as the DataTable's `headerView` attribute (the default, as set by `datatable-base`). | yes
`datatable-body` | Creates the `Y.DataTable.BodyView` class as a subclass of `Y.View`. DataTable defers rendering of the `<tbody>` content to this View when it is passed as the DataTable's `bodyView` attribute (the default, as set by `datatable-base`). | yes
`datatable-message` | Creates the `Y.DataTable.Message` class extension and adds `showMessage` and `hideMessage` methods to `Y.DataTable`. | yes
`datatable-column-widths` | Creates the `Y.DataTable.ColumnWidths` class extension, and adds support for the `width` property in column configuration objects to `Y.DataTable`. | yes
`datatable-mutable` | Creates the `Y.DataTable.Mutable` class extension and adds methods such as `addRow`, `removeRow`, and `moveColumn` to `Y.DataTable`. | yes
`datatable-sort` | Creates the `Y.DataTable.Sortable` class extension and adds methods `sort` and `toggleSort` as well as attributes `sortable` and `sortBy` to `Y.DataTable`. Enables sorting the table rows by clicking on column headers. | yes
`datatable-datasource` | Creates the `Y.Plugin.DataTableDataSource` plugin for binding a DataSource instance to the table as its source of record data. | yes
`datatable-scroll` | Creates the `Y.DataTable.Scroll` class extension and adds attribute `scrollable` to `Y.DataTable`. Adds support for vertically and/or horizontally scrolling table rows within fixed table dimensions. | no
`datatable-formatters` | Populates `Y.DataTable.BodyView.Formatters` with a collection of cell formatting functions. | no

### Features in `DataTable.Base`

By including only `datatable-base` in your `use()` line, you get both `Y.DataTable` and `Y.DataTable.Base` classes. With no other module inclusion, these classes are effectively the same. When additional DataTable related modules are included, those modules' features will usually be added to `Y.DataTable`, but never to `Y.DataTable.Base`.

Though it can be instantiated, the purpose of `Y.DataTable.Base` is primarily as a superclass to a custom DataTable implementation that has a locked set of features that will not be modified, as `Y.DataTable` can be, by the inclusion of other modules.

    // Create a custom DataTable that includes only the core set of APIs, plus
    // sorting and message support.
    Y.MyDataTable = Y.Base.create('myTable', Y.DataTable.Base,
        [ Y.DataTable.Sortable, Y.DataTable.Message ]);

    Y.use('datatable-scroll', function (Y) {
        // Y.DataTable now has support for scrolling
        var table = new Y.DataTable({ scrollable: 'y', ... });

        // Y.MyDataTable does not (the config does nothing)
        var myTable = new Y.MyDataTable({ scrollable: 'y', ... });
    });

`Y.DataTable.Base` includes the `columns`, `data`, `caption`, and other basic table attributes, the underlying ModelList and View rendering architecture, as well as methods to fetch rows and cells or columns and records.

Rendering features include most column configurations, such as `children` and `allowHTML`, as well as column formatting options `formatter`, `nodeFormatter`, `cellTemplate`, etc.

### Table Messages

The `datatable-message` module adds the ability to display a message in the table body. By default, the "emptyMessage" will display when the table's ModelList has no data records. The message will hide when data is added.

    var table = new Y.DataTable({
        columns: ["id", "name", "price"],
        data: []
    }).render('#example');

This code produces this table:

Use `table.showMessage("message")` and `table.hideMessage()` to toggle the message display.

`showMessage` supports internationalized strings by using a few named strings, which are registered in the language packs for the `datatable-message` module . These strings are currently:

- `table.showMessage("emptyMessage")` defaults to "No data to display".
- `table.showMessage("loadingMessage")` defaults to "Loading...".

Other values passed to `showMessage` will pass that content directly through to the message Node.

### Column Width Configuration

The `datatable-column-widths` module adds basic support for specifying column widths.

    var table = new Y.DataTable({
        columns: [
            { key: 'item', width: '125px' },
            { key: 'cost', formatter: '${value}' },
            ...
        ],
        data   : data
    }).render("#example");

This code produces this table:

CAVEAT: Column widths will expand beyond the configured value if column cells contain data that is long and can't line-wrap. Also, column widths may be reduced below the configured value if the table width (by configuring the DataTable's `width` attribute, or constrained by a narrow containing element) is too narrow to fit all data at the configured widths.

To force column widths, including cell data truncation and allowing the table to spill beyond its configured or inherited width, wrap the cell content in a `<div>` either by configuring the column's `formatter` or `cellTemplate`, then assign the `<div>`'s CSS style with the desired width (or "inherit"), plus `overflow: hidden;`. Then set the DataTable column's `width` configuration accordingly.

### Column sorting

The `datatable-sort` module adds support for sorting the table rows either through the added APIs or by clicking on the table headers.

By default, when `datatable-sort` is included, DataTables will inspects the `columns` objects, looking for `sortable: true` to enable table sorting by those columns, triggered by clicking on their respective headers.

    var cols = [
        { key: "Company", sortable: true },
        { key: "Phone" },
        { key: "Contact", sortable: true }
    ];

For convenience, you can enable header-click sorting for all columns by setting the `sortable` attribute to `true`, or pass an array of column keys to enable just those column's headers.

    // Set all columns to be sortable
    var table = new Y.DataTable({
        columns: ["Company", "Phone", "Contact"],
        data: ...
        sortable: true
    }).render("#example");

This code produces this table:

Hold down the `shift` key while clicking on column headers to subsort by that column. Doing so repeatedly will toggle the subsort direction.

As long as the `datatable-sort` module has been included, you will always be able to sort the table data through the API, even by columns that aren't configured to accept header-click sorting.

When a table is sorted, any new records added to the DataTable's ModelList will be inserted at the proper sorted index, as will the created table rows.

Disable header-click sorting by setting `sortable` to `false`.

The default sort order is case insensitive, the sort order can be set to case sensitive by using the `caseSensitive` attribute, see Appendix A below.

#### Custom Sorting

Assign a function to a column's `sortFn` to support customized sorting. The function will receive the two records being compared and a boolean flag indicating a descending sort was requested.

    var columns = [
        {
            key: 'id',
            label: '&#9679;', // a big dot
            formatter: function (o) {
                return o.value ? '' : '&#9679;'; // only new records have a dot
            },
            sortable: true,
            sortFn: function (a, b, desc) {
                var aid   = a.get('id'),
                    bid   = b.get('id'),
                    acid  = a.get('clientId'),
                    bcid  = b.get('clientId'),
                    order = // existing records are equivalent
                            (aid && bid) ? 0 :
                            // new records are grouped apart from existing records
                            (aid && -1) || (bid && 1) ||
                            // new records are sorted by insertion order
                            (acid > bcid) ? 1 : -(acid < bcid);

                return desc ? -order : order;
            }
        },
        ...

The function must return 1, 0, or -1. 1 specifies that the Model passed as the first parameter should sort below the Model passed as the second parameter. -1 for above, and 0 if they are equivalent for the purpose of this sort.

#### Sorting Methods

To sort the table in the code, call `table.sort(NAME OR KEY)`. To toggle the sort direction, call `table.toggleSort(NAME OR KEY)`.

    // Sorts the table by values in the price field in ascending order
    table.sort('price');

    // Flips to descending
    table.toggleSort('price');

To sort by multiple columns, pass an array of column keys to `sort` or `toggleSort`.

Calling `toggleSort` with no arguments will reverse all current sort directions. Calling with specific column names or keys will toggle only those columns.

    // Sort first by author, subsort by title in ascending order
    table.sort(['author', 'title']);

    // Now descending by author then title
    // same as table.toggleSort(['author', 'title']);
    table.toggleSort();

    // Now ascending by author, descending by title
    table.toggleSort('author');

To specify a sort direction, pass an object instead of a string to `sort`. The object should have the column name as the key, and sort direction as its value.

    // Explicitly sort by price in descending order
    table.sort({ price: 'desc' });

    // Each column gets its own object
    table.sort([{ author: 'desc' }, { title: 'desc' }]);

Acceptable values for the sort direction are "asc", "desc", 1, and -1. 1 is equivalent to "asc", and -1 to "desc".

#### The `sortBy` Attribute

Every sort operation updates the `sortBy` attribute. You can also trigger a sort by setting this attribute directly. It accepts the same values as the `sort` method.

    // Sort by author in descending order, then by title in ascending order
    table.set('sortBy', [{ author: -1 }, 'title']);

To specify an initial sort order for your table, assign this attribute during instantiation. This will sort the data as soon as it is added to the table's ModelList.

    // Pre-sort the data
    var table = new Y.DataTable({
        columns: ['item', 'cost', 'price'],
        data: [...],
        sortBy: { price: -1 }
    });

#### The `sort` Event

Clicking on a column header, or calling the `sort` or `toggleSort` methods will fire a `sort` method containing an `e.sortBy` property that corresponds to the requested sort column and direction. The value will be in either string or object format, depending on how each method was used.

Preventing the `sort` event will prevent the `sortBy` attribute from being updated. Updating the `sortBy` attribute directly will not fire the `sort` event, but will still sort the data and update the table.

### Table Mutation APIs (`addRow`, etc)

The `datatable-mutable` module adds APIs for adding, removing, and modifying records and columns.

#### Column Mutation Methods

Use the methods `addColumn`, `removeColumn`, `modifyColumn`, and `moveColumn` to update the table's configured `columns`.

    // Insert a column for the profit field in the data records as the third column
    table.addColumn('profit', 2);

    // Actually, make that the fourth column
    table.moveColumn('profit', 3);

    // Actually, strike that.  Don't show it after all
    table.removeColumn('profit');

    // Instead, add a formatter to the price column that includes the profit data
    table.modifyColumn('price', {
        formatter: function (o) {
            return o.value + ' (' + (o.data.profit / o.data.cost).toFixed(2) + '%)';
        }
    });

Each column mutation method fires an identically named event. See the API docs for details.

#### Row Mutation Methods

Use the methods `addRow`, `addRows`, `removeRow`, and `modifyRow` to update the table's ModelList.

    table.addRow({ item: 'collet', cost: 0.42, price: 2.65 });

    table.addRows([
        { item: 'nut',    cost: 0.42, price: 2.65 },
        { item: 'washer', cost: 0.01, price: 0.08 },
        { item: 'bit',    cost: 0.19, price: 0.97 }
    ]);

    // Remove table records by their Model, id, clientId, or index
    table.removeRow(0);

    // Modify a record by passing its id, clientId, or index, followed by an
    // object with new field values
    table.modifyRow('record_4', { cost: 0.74 });

Everything that's done by these methods can be accomplished through the table's ModelList instance methods, but having methods on the table itself can make the code more readable.

    // Same as table.addRow(...);
    table.data.add({ item: 'collet', cost: 0.42, price: 2.65 });

By default, changes made to the table are only local, they don't update the server or other data origin if the data was served remotely. However, if your table's ModelList is built with a sync layer, the mutation methods can also trigger the appropriate sync behavior by passing an additional argument to the methods, an object with the property `sync` set to `true`.

    // Tell the server we're down to one slice of apple pie!
    table.modifyRow('apple', { slices: 1 }, { sync: true });

    // Uh oh, make that 0.  No more apple pie :(
    table.removeRow('apple', { sync: true });

If all modifications are destined for the server/origin, you can set the `autoSync` attribute to `true`, and the row mutation methods will automatically call into the sync layer.

    var pies = new Y.DataTable({
        columns: ['type', 'slices'],
        data: new Y.PieList()
        autoSync: true
    });

    pies.data.load(function () {

        pies.render('#pie-cart');

        // The new PieModel's save() method is called, notifying the server
        pies.addRow({ type: 'pecan', slices: 8 });

        // Let us eat some pie!
        pies.modifyRow('lemon meringue', { slices: 5 });
    });

### Scrolling

Note: Scrolling is not currently supported on the Android WebKit browser.

Scrolling functionality can be added to `Y.DataTable` by including `datatable-scroll` module in your `use()`. `datatable-scroll` is NOT included in the `datatable` rollup module, so must be included separately.

Enable scrolling by setting the `scrollable` attribute, which accepts values "x", "y", "xy", `true` (same as "xy"), or `false` (the default).

Note, vertical scrolling also requires the table's `height` attribute to be set, and horizontal scrolling requires the `width` to be set.

    // Data from the seafoodwatch YQL table as of 3/16/2012
    var data = [
        { "fish": "Barramundi (Imported Farmed in Open Systems)", "recommendation": "avoid" },
        { "fish": "Caviar, Paddlefish (Wild caught from U.S.)", "recommendation": "avoid" },
        { "fish": "Caviar, Sturgeon (Imported Wild-caught)", "recommendation": "avoid" },
        ...
    ];

    // Enable vertical scrolling with scrollable "y". The width is also set, but
    // because scrollable is not "x" or "xy", this just sets the table width.
    var table = new Y.DataTable({
        caption: 'Seafood tips for the US West Coast',
        columns: ['fish', 'recommendation'],
        data: data,
        scrollable: "y",
        height: "200px",
        width:  "400px"
    }).render("#scroll");

This code produces this table:

## DataTable Events

DataTable is a composition of supporting class instances and extensions, so to centralize event reporting, it is a bubble target for its `data` ModelList as well as the View instances used for rendering.

In other words, some events you may need to subscribe to using an event prefix to be notified. Often, using a wildcard prefix is the simplest method to ensure your subscribers will be notified, even if classes change.

    // The sort event is from an extension, so it originates from DataTable
    table.after('sort', function (e) { ... });

    // Model changes originate from the record's Model instance, propagate to the
    // table's ModelList, then finally to the DataTable, so they must be
    // subscribed with an event prefix.  In this case, we'll use a wildcard
    // prefix.
    table.after('*:priceChange', function (e) { ... });

DataTable generates a custom Model class with the "record" event prefix, if you want to be more specific. Otherwise, if your table uses a custom Model class for its `recordType`, you can prefix Model events with the appropriate prefix.

    // Allow DataTable to generate the Model class automatically
    var table = new Y.DataTable({
        columns: ['items', 'cost', 'price'],
        data: [
            { item: "widget", cost: 23.57, price: 47.5 },
            { item: "gadget", cost: 0.11, price: 6.99 },
            ...
        ]
    });

    // generated Model classes have prefix "record"
    table.after('record:change', function (e) { ... });

    // PieList uses PieModels, which have a prefix of, you guessed it, "pie"
    var pies = new Y.DataTable({
        columns: ['type', 'slices'],
        data: new Y.PieList()
    });

    pies.on('pie:slicesChange', function (e) {
        if (e.target.get('type') === 'chocolate creme') {
            // Oh no you don't!
            e.preventDefault();
        }
    });

The full list of events is included in the DataTable API docs.

## Known Issues

- Scrolling is not currently supported on Android WebKit browser.
- Scrolling DataTable may not appear scrollable on iOS browsers or OS X 10.7 depending on the system preference "Show scroll bars" (General).

## Appendix A: Column Configurations

The properties below are supported in the column configuration objects passed in the `columns` attribute array.

Configuration | Description | Module
--- | --- | ---
key |
    { key: 'username' }
Binds the column values to the named property in the `data`. Optional if `formatter`, `nodeFormatter`, or `cellTemplate` is used to populate the content. It should not be set if `children` is set. The value is used for the `_id` property unless the `name` property is also set. | `datatable-base`
name |
    { name: 'fullname', formatter: ... }
Use this to assign a name to pass to `table.getColumn(NAME)` or style columns with class "yui3-datatable-col-NAME" if a column isn't assigned a `key`. The value is used for the `_id` property. | `datatable-base`
field |
    { field: 'fullname', formatter: ... }
An alias for `name` for backward compatibility. | `datatable-base`
id |
    {
      name: 'checkAll',
      id: 'check-all',
      label: ...
      formatter: ...
    }
Overrides the default unique id assigned `<th id="HERE">`. Use this with caution, since it can result in duplicate ids in the DOM. | `datatable-base`
label |
    { key: 'MfgPrtNum', label: 'Part Number' }
HTML to populate the header `<th>` for the column. | `datatable-base`
children | Used to create stacked headers. See the example above. Child columns may also contain `children`. There is no limit to the depth of nesting. Columns configured with `children` are for display only and should not be configured with a `key`. Configurations relating to the display of data, such as `formatter`, `nodeFormatter`, `emptyCellValue`, etc. are ignored. | `datatable-base`
abbr |
    {
      key  : 'forecast',
      label: '1yr Target Forecast',
      abbr : 'Forecast'
    }
Assigns the value `<th abbr="HERE">`. | `datatable-base`
title |
    {
      key  : 'forecast',
      label: '1yr Target Forecast',
      title: 'Target Forecast for the Next 12 Months'
    }
Assigns the value `<th title="HERE">`. | `datatable-base`
headerTemplate |
    {
      headerTemplate:
        '<th id="{id}" ' +
            'title="Unread" ' +
            'class="{className}" ' +
            '{_id}>&#9679;</th>'
    }
Overrides the default CELL_TEMPLATE used by `Y.DataTable.HeaderView` to render the header cell for this column. This is necessary when more control is needed over the markup for the header itself, rather than its content. Use the `label` configuration if you don't need to customize the `<th>` iteself. Implementers are strongly encouraged to preserve at least the `{id}` and `{_id}` placeholders in the custom value. | `datatable-base`
cellTemplate |
    {
      key: 'id',
      cellTemplate:
        '<td class="{className}">' +
          '<input type="checkbox" ' +
                 'id="{content}">' +
        '</td>'
    }
Overrides the default CELL_TEMPLATE used by `Y.DataTable.BodyView` to render the data cells for this column. This is necessary when more control is needed over the markup for the `<td>` itself, rather than its content. | `datatable-base`
formatter | Used to customize the content of the data cells for this column. See the example above | `datatable-base`
nodeFormatter | Used to customize the content of the data cells for this column. See the example above | `datatable-base`
emptyCellValue |
    {
      key: 'price',
      emptyCellValue: '???'
    }
Provides the default value to populate the cell if the data for that cell is `undefined`, `null`, or an empty string. | `datatable-base`
allowHTML |
    {
      key: 'preview',
      allowHTML: true
    }
Skips the security step of HTML escaping the value for cells in this column. This is also necessary if `emptyCellValue` is set with an HTML string. `nodeFormatter`s ignore this configuration. If using a `nodeFormatter`, it is recommended to use Y.Escape.html() on any user supplied content that is to be displayed. | `datatable-base`
className |
    {
      key: 'symbol',
      className: 'no-hide'
    }
A string of CSS classes that will be added to the `<td>`'s `class` attribute. Note, all cells will automatically have a class in the form of "yui3-datatable-col-KEY" added to the `<td>`, where KEY is the column's configured `name`, `key`, or `id` (in that order of preference). | `datatable-base`
width |
    { key: 'a', width: '400px' },
    { key: 'b', width: '10em' }
Adds a style `width` setting to an associated `<col>` element for the column. Note, the assigned width will not truncate cell content, and it will not preserve the configured width if doing so would compromise either the instance's `width` configuration or the natural width of the table's containing DOM elements. If absolute widths are required, it can be accomplished with some custom CSS and the use of a `cellTemplate`, or `formatter`. See the description of `datatable-column-widths` for an example of how to do this. | `datatable-column-widths`
sortable |
    { key: 'lastLogin', sortable: true }
Used when the instance's `sortable` attribute is set to "auto" (the default) to determine which columns will support user sorting by clicking on the header. If the instance's `key` attribute is not set, this configuration is ignored. | `datatable-sort`
caseSensitive |
    { key: 'lastLogin', sortable: true, caseSensitive: true }
When the instance's `caseSensitive` attribute is set to "true" the sort order is case sensitive (relevant to string columns only). Case sensitive sort is marginally more efficient and should be considered for large data sets when case insensitive sort is not required. | `datatable-sort`
sortFn |
    {
      label: 'Name',
      sortFn: function (a, b, desc) {
        var an = a.get('lname') + b.get('fname'),
            bn = a.get('lname') + b.get('fname'),
            order = (an > bn) ? 1 : -(an < bn);

        return desc ? -order : order;
      },
      formatter: function (o) {
        return o.data.lname + ', ' + o.data.fname;
      }
    }
Allows a column to be sorted using a custom algorithm. The function receives three parameters, the first two being the two record Models to compare, and the third being a boolean `true` if the sort order should be descending. The function should return `-1` to sort `a` above `b`, `-1` to sort `a` below `b`, and `0` if they are equal. Keep in mind that the order should be reversed when `desc` is `true`. The `desc` parameter is provided to allow `sortFn`s to always sort certain values above or below others, such as always sorting `null`s on top. | `datatable-sort`
sortDir | (read-only) If a column is sorted, this will be set to `1` for ascending order or `-1` for descending. This configuration is public for inspection, but can't be used during DataTable instantiation to set the sort direction of the column. Use the table's sortBy attribute for that. | `datatable-sort`
_yuid | (read-only) The unique identifier assigned to each column. This is used for the `id` if not set, and the `_id` if none of `name`, 'field`,` key`, or` id` are set. | `datatable-base`
_id | (read-only) A unique-to-this-instance name used extensively in the rendering process. It is also used to create the column's classname, as the input name `table.getColumn(HERE)`, and in the column header's `<th data-yui3-col-id="HERE">`. The value is populated by the first of `name`, `field`, `key`, `id`, or `_yuid` to have a value. If that value has already been used (such as when multiple columns have the same `key`), an incrementer is added to the end. For example, two columns with `key: "id"` will have `_id`s of "id" and "id2". `table.getColumn("id")` will return the first column, and `table.getColumn("id2")` will return the second. | `datatable-base`
_colspan | (read-only) Used by `Y.DataTable.HeaderView` when building stacked column headers. | `datatable-base`
_rowspan | (read-only) Used by `Y.DataTable.HeaderView` when building stacked column headers. | `datatable-base`
_parent | (read-only) Assigned to all columns in a column's `children` collection. References the parent column object. | `datatable-base`
_headers | (read-only) Array of the `id`s of the column and all parent columns. Used by `Y.DataTable.BodyView` to populate `<td headers="THIS">` when a cell references more than one header. | `datatable-base`

## Appendix B: Formatter Argument Properties

The properties below are found on the object passed to `formatter` functions defined in a column configuration. See Appendix C for the object properties passed to `nodeFormatter`s.

Property | Description
--- | ---
`value` |
    formatter: function (o) {
        // assumes a numeric value for this column
        return '$' + o.value.toFixed(2);
    }
The raw value from the record Model to populate this cell. Equivalent to `o.record.get(o.column.key)` or `o.data[o.column.key]`.
`data` |
    formatter: function (o) {
        return o.data.lname + ', ' + o.data.fname;
    }
The Model data for this row in simple object format.
`record` |
    formatter: function (o) {
        return '<a href="/service/' + o.record.get('id') + '">' +
            o.value + '</a>';
    }
The Model for this row.
`column` |
    formatter: function (o) {
        // Use a custom column property
        var format = o.column.dateFormat || '%D';

        return Y.DataType.Data.format(o.value, format);
    }
The column configuration object.
`className` |
    formatter: function (o) {
        if (o.value < 0) {
            o.className += 'loss';
        }
    }
A string of class names to add `<td class="HERE">` in addition to the column class and any classes in the column's `className` configuration.
`rowIndex` |
    formatter: function (o) {
        return (o.rowIndex + 1) + ' - ' + o.value;
    }
The index of the current Model in the ModelList. Typically correlates to the row index as well.
`rowClass` |
    formatter: function (o) {
        if (o.value < 0) {
            o.rowClass += 'loss';
        }
    }
A string of css classes to add `<tr class="HERE"><td...`. This is useful to avoid the need for `nodeFormatter`s to add classes to the containing row.

## Appendix C: nodeFormatter Argument Properties

The properties below are found on the object passed to `nodeFormatter` functions defined in a column configuration. See Appendix B for the object properties passed to `formatter`s.

    // Reference nodeFormatter
    nodeFormatter: function (o) {
        if (o.value < o.data.quota) {
            o.td.setAttribute('rowspan', 2);
            o.td.setAttribute('data-term-id', this.record.get('id'));

            o.td.ancestor().insert(
                '<tr><td colspan"3">' +
                    '<button class="term">terminate</button>' +
                '</td></tr>',
                'after');
        }

        o.cell.setHTML(o.value);
    }

Property | Description
--- | ---
`td` | The `<td>` Node for this cell.
`cell` | If the cell `<td>` contains an element with class "yui3-datatable-liner", this will refer to that Node. Otherwise, it is equivalent to `o.td` (default behavior). By default, liner elements aren't rendered into cells, but to implement absolute column widths, some cell liner element with `width` and `overflow` style is required (barring a table style of `table-layout: fixed`). This may be applied to the columns `cellTemplate` configuration or to the `bodyView` instance's `CELL_TEMPLATE` for all columns. Generally, the liner, if present, corresponds to where the content should go, so use `o.cell` to add content and `o.td` to specifically work with the `<td>` Node.
`value` | The raw value from the record Model to populate this cell. Equivalent to `o.record.get(o.column.key)` or `o.data[o.column.key]`.
`data` | The Model data for this row in simple object format.
`record` | The Model for this row.
`column` | The column configuration object.
`rowIndex` | The index of the current Model in the ModelList. Typically correlates to the row index as well.