Исключение, пойманное библиотекой виджетов

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div id="example" style="border: 1px solid rgb(204, 204, 204); margin: 5px 0pt; padding: 5px;">Example div</div>
<form>
    <div><textarea class="example-default-value" id="example-textarea" style="width: 400px; height: 50px;">Type some text in here to be appended</textarea></div>
    <div><input type="button" value="Append" onclick="example_append()" /></div>
</form>
<script language="javascript">
$('.example-default-value').each(function() {
    var default_value = this.value;
    $(this).focus(function() {
        if(this.value == default_value) {
            this.value = '';
        }
    });
    $(this).blur(function() {
        if(this.value == '') {
            this.value = default_value;
        }
    });
});
function example_append() {
    $('#example').append($('#example-textarea').val());
}
</script>