Defines a kendo template that will be used as the card header inside the popover component.

Example - setting the template as string

<span id="target">
    Some Content
</span>

<script>
    $(document).ready(function() {
      $("#target").kendoPopover({
        header: "Header content",
        body: "Content description"
    });
</script>

Example - setting the template as function

<span id="target">
    Some Content
</span>

<script>
    $(document).ready(function() {
      $("#target").kendoPopover({
        header: function (e) {
          return e.target.text() + " header";
        },
        body: function (e) {
          return e.target.text() + " description";
        }
      });
    });
</script>
In this article