index Number(default: -1)

The index of the initially selected item. The index is 0 based.

Example - select second item

<input id="combobox" />
<script>
var items = [{ text: "Item 1", value: "1" }, { text: "Item 2", value: "2" }];
$("#combobox").kendoComboBox({
    dataTextField: "text",
    dataValueField: "value",
    dataSource: items,
    index: 1
});
</script>