Validate .NET control and javascript confim before postback

< asp:imagebutton id="ibDelete" causesvalidation="true" onclientclick="return checkDelete()" validationgroup="ModalValidation" alternatetext="Delete Journal" runat="server" imageurl="~/images/icons/delete.gif" onclick="ibDelete_Click"/>

function checkDelete(){
if(Page_ClientValidate())
{
var record=confirm('Are you sure you want to delete this record?');
if(record == 1)
{
return true;
}
else if(record == 0)
{
return false;
}
}
}