var vizDivObject = document.getElementById('tableauVizDiv');
var options = {
width: vizDivObject.offsetWidth,
height: "500px", //vizDivObject.offsetHeight,
hideTabs: true,
hideToolbar: true
};
<div id="tableauVizDiv" style="width: 1304px; height: 862px;"></div>
var workbook = viz.getWorkbook();
var activeSheet = workbook.getActiveSheet();
if (activeSheet.getSheetType() === 'dashboard') { //worksheet or dashboard
//alert(activeSheet.getName());
activeSheet.changeSizeAsync({
behavior: tableauSoftware.SheetSizeBehavior.AUTOMATIC
});
}