<div id="spreadsheet"></div>
<script>
var spreadsheet = $("#spreadsheet").kendoSpreadsheet({
    sheets: [
        { name: "Sheet1" },
        { name: "MyData" },
        { name: "Sheet3" }
    ]
}).data("kendoSpreadsheet");

var sheet = spreadsheet.sheetByName("MyData");
var index = spreadsheet.sheetIndex(sheet);
console.log("Sheet index:", index);
</script>