如何避免AJAX成功函数中的未定义错误消息

Sometimes, data returned from the server is not defined which results in the following appearing on my page:

<p id="element">undefined</p>

My AJAX success function:

success: function( data ) {
    $( '#element' ).text( data.message )
}

PHP handler:

$response = array()

// Some logic which may assign data to $response['message']

echo json_encode( $response );
die;

Is there a way to suppress such undefined messages?

Depending on what you want, you can show message only if it was provided

if (data.message) {
    $('#element').text(data.message)
}

or maybe show default message if server returns nothing (or empty string):

$('#element').text(data.message || 'No message.')    

success: function( data ) {

    if( data.message !== undefined )
        $( '#element' ).text( data.message )

}