In the Data Source

Items in the List are grouped if they are grouped in the data source. The List recognizes a group when it encounters an object with the key and items fields. The key is the group header, the items are items that fell into the group. For example, the fruitsVegetables array from the following code produces two groups with three items each. Note that the List needs to be informed that it deals with grouped data, therefore its grouped option is set to true.

JavaScript
var fruitsVegetables = [{
    key: "Fruits",
    items: [
        { name: "Apples", count: 10 },
        { name: "Oranges", count: 12 },
        { name: "Lemons", count: 15 }
    ]
}, {
    key: "Vegetables",
    items: [
        { name: "Potatoes", count: 5 },
        { name: "Tomatoes", count: 9 },
        { name: "Turnips", count: 8 }
    ]
}];

$(function() {
    $("#listContainer").dxList({
        dataSource: fruitsVegetables,
        grouped: true,
        itemTemplate: function(data, _, element) {
            element.append(
                $("<p>").text(data.name + " | " + data.count).css("margin", 0)
            )
        }
    });
});

View Demo

If objects in your data source miss the key and items fields, use the map function of the DevExtreme DataSource to bring these objects to the key + items structure. You can find more information on the map function in the Data Layer - Item Mapping topic.

JavaScript
var fruitsVegetables = [{
    type: "Fruits",
    collection: [
        { name: "Apples", count: 10 },
        { name: "Oranges", count: 12 },
        { name: "Lemons", count: 15 }
    ]
}, {
    type: "Vegetables",
    collection: [
        { name: "Potatoes", count: 5 },
        { name: "Tomatoes", count: 9 },
        { name: "Turnips", count: 8 }
    ]
}];

$(function() {
    $("#listContainer").dxList({
        dataSource: new DevExpress.data.DataSource({
            store: fruitsVegetables,
            map: function(item) {
                return {
                    key: item.type,
                    items: item.collection
                }
            }
        }),
        grouped: true,
        itemTemplate: function(data, _, element) {
            element.append(
                $("<p>").text(data.name + " | " + data.count).css("margin", 0)
            )
        }
    });
});

If your data is not grouped at all, you can group it using the group option of the DataSource. See the Data Layer - Grouping topic for details.

JavaScript
var fruitsVegetables = [
    { type: "Fruits", name: "Apples", count: 10 },
    { type: "Fruits", name: "Oranges", count: 12 },
    { type: "Fruits", name: "Lemons", count: 15 },
    { type: "Vegetables", name: "Potatoes", count: 5 },
    { type: "Vegetables", name: "Tomatoes", count: 9 },
    { type: "Vegetables", name: "Turnips", count: 8 }
];

$(function() {
    $("#listContainer").dxList({
        dataSource: new DevExpress.data.DataSource({
            store: fruitsVegetables,
            group: "type"
        }),
        grouped: true,
        itemTemplate: function(data, _, element) {
            element.append(
                $("<p>").text(data.name + " | " + data.count).css("margin", 0)
            )
        }
    });
});
See Also