Jquery检查数组计数并获取数组索引名称

Question

I am working on my jquery code to count on how many data I have and fetch the filename name from the PHP array. I have the return output for result.data.attachment which it show [object Object].

$.ajax({
    url: 'readDraft.php',
    type: 'POST',
    data : {
        email_number: email_number
    },
    dataType: 'json',

    success: function(result) {
        alert(result.data.attachment);
    }
 });

Here is the full code for ajax function:

$(document).on('click','#openDraft', function(e) {
    e.preventDefault();
    var email_number = $(this).closest('tr').attr('data-id');
    var encryptedAES = $(this).closest('tr').attr('data-url');
    var id = Math.round((Math.random() * 36 ** 12)).toString(36);


    if ($("#movetoFolder").css('display') == 'block') {
        $('#movetoFolder').hide();
    }
    total_compose.push(id);
    compose_count++;


    for (var i = 0; i < total_compose.length; i++)
    {
        var popup_class = "popup-window-"+total_compose[i];
        $('#'+popup_class).hide();
        newMail("", id, compose_count);
    }
    var popup_class = "popup-window-"+total_compose[total_compose.length-2];
    var popup_window = "popup-window-"+id;
    email_receipt = $('#domodal_email_receipt').val();
    email_subject = $('#domodal_subject').val();
    email_message = $('#domodal_message').val();

    $.ajax({
        url: 'readDraft.php',
        type: 'POST',
        data : {
            email_number: email_number
        },
        dataType: 'json',

        success: function(result) {
            alert(result);

            if (result.data.receipt != '') {
                $("#domodal_email_receipt").val(result.data.receipt);
            }

            if (result.data.subject != '') {
                $("#domodal_subject").val(result.data.subject);
            }

            if (result.data.message != '') {
                $("#domodal_message").text(result.data.message);
            }

            if (result.data.attachment > 0) {
                var fileName = result.data.attachment['filename'];
                alert("here!");
                alert(result.data.attachment);
                alert(result.data.attachment['filename']);

                //var add_attachment = '<div class="dL" tabindex="-1" id="vw" aria-label="Attachment: '+fileName+'. Press enter to view the attachment and delete to remove it" style="position:relative;"><div style="display:flex"><a class="dO" id="attach_url'+attach_url_id+ '" href="http://test.example.com/u/?id=&attid=0&msg=6685135251679589431&view=att&disp=safe" target="_blank" style="display:flex;"><div id="domodal_attachment" class="vI">'+fileName+'</div><div class="vJ">'+fileSize+'</div></a><div id="vn" role="button" aria-label="Remove attachment" class="vq" tabindex="-1" data-tooltip="Remove attachment" style="position:absolute; right:5px; top:5px;"></div></div></div>';

                //$('.file-list_yhs').append(add_attachment);
            }
        }
    });
    window.history.pushState("object or string", "Title", "http://test.example.com/#draft/"+encryptedAES);
    $('#'+popup_class).show();
});

Here is the readDraft.php:

<?php

$structure = imap_fetchstructure($draft, $email_number);
$overview = imap_fetch_overview($draft, $email_number);
$draft_from = $overview[0]->from;
$draft_to = $overview[0]->to;
$draft_subject = utf8_decode(imap_utf8($overview[0]->subject));
$draft_fulldate = $overview[0]->date;
$draft_date = convDate($draft_fulldate);
$draft_message = quoted_printable_decode(imap_fetchbody($draft, $email_number, 1.2));
$attachments = array();

if(isset($structure->parts) && count($structure->parts)) {

    for($i = 0; $i < count($structure->parts); $i++) {

        if($structure->parts[$i]->ifdparameters) {
            foreach($structure->parts[$i]->dparameters as $object) {
                if(strtolower($object->attribute) == 'filename') {
                    $attachments[$i]['is_attachment'] = true;
                    $attachments[$i]['filename'] = $object->value;
                }
            }
        }

        if($structure->parts[$i]->ifparameters) {
            foreach($structure->parts[$i]->parameters as $object) {
                if(strtolower($object->attribute) == 'name') {
                    $attachments[$i]['is_attachment'] = true;
                    $attachments[$i]['name'] = $object->value;
                }
            }
        }

        if($attachments[$i]['is_attachment']) {
            $attachments[$i]['attachment'] = imap_fetchbody($connection, $message_number, $i+1);
            if($structure->parts[$i]->encoding == 3) { // 3 = BASE64
                $attachments[$i]['attachment'] = base64_decode($attachments[$i]['attachment']);
            }
            elseif($structure->parts[$i]->encoding == 4) { // 4 = QUOTED-PRINTABLE
                $attachments[$i]['attachment'] = quoted_printable_decode($attachments[$i]['attachment']);
            }
        }
    }
}

$data = array("receipt"=>$draft_to, "subject"=>$draft_subject, "encryption"=>$email_number_encrypt, "message"=>$draft_message, "attachment"=>$attachments);
$response = array("data"=>$data, "success"=>"successfully", "total_inbox"=>$total_inbox_unread, "total_spam"=>$total_spam_unread);
echo json_encode($response);
?>

Output for readDraft.php attachment:

Array
(
    [1] => Array
      (
         [is_attachment] => 1
         [filename] => draft_attachment.rar
         [name] => draft_attachment.rar
         [attachment] =>
      )
)


Array
(
    [2] => Array
      (
         [is_attachment] => 1
         [filename] => draft_attachment - Copy.rar
         [name] => draft_attachment - Copy.rar
         [attachment] =>
      )
)

I have tried this:

success: function(result) {
    if (result.data.attachment.length > 0) {
        ...do something
    }
}

It wont let me to get pass on the if statement. I have also tried this which it didn't work:

if (result.data.attachment > 0) {
   ...do something
}

What I am trying to do is I want to check on result.data.attachment that if I have one or more attachment then I want to fetch the attachments filename.

Can you please show me an example how I could be able to check if I have one attachment or more and how I can also fetch the filename from the attachments array?

Thank you.