How to check the compliance of the VKontakte repost?

Question

JavaScript

vk.com/dev/wall.getById
A person enters the ID of his repost, I want to check that he reposted my post.
For example vk.com/durov?w=wall1_593585 and vk.com/pavel_durov_quotes?w=wall-51370128_38085 upon request

VK.Api.call('wall.getById', {posts: '-51370128_38085', copy_history_depth: 999}, function(r) { 
// code
});

will return

response: [{
id: 38085,
from_id: -51370128,
owner_id: -51370128,
date: 1448435117,
post_type: 'post',
text: 'Комментарий Павла по поводу статьи в издании "Секрет Фирмы". #durov #павелдуровИздание «Секрет фирмы» опубликовало рейтинг самых успешных молодых предпринимателей возрастом до 40 лет с российским гражданством. Лидером списка стал основатель «ВКонтакте» и Telegram Павел Дуров.«Секрет фирмы» выстроил рейтинг по уменьшению стоимости доли предпринимателя в его бизнесе. Лидер списка, 31-летний Павел Дуров, целиком контролирует Telegram, который издание оценило в $1 млрд. Сам Дуров полагает, что его компания стоит около $3-4 млрд.На втором месте — 39-летний Иван Таврин, гендиректор «Мегафона» и совладелец «ЮТВ Холдинга», в котором ему принадлежит 50%. Его долю издание оценило в $400 млн.Третье и четвёртое место заняли братья Семён и Ефим Войновы (обоим по 33 года), их доли в разработчике игр Zeptolab оценены в $250 млн. На пятом месте — 38-летний основатель поисковика авиабилетов OneTwoTrip Пётр Кутис ($130 млн).',
copy_history: [{
id: 593585,
owner_id: 1,
from_id: 1,
date: 1448431475,
post_type: 'post',
text: 'Можно ли дать рыночную оценку тому, что не продается?',
attachments: [{
type: 'link',
link: {
url: 'https://vc.ru/p/sf-young-rating-2015',
title: 'Павел Дуров возглавил рейтинг самых успешных бизнесменов России до 40 лет по версии «Секрета фирмы»',
caption: 'vc.ru',
description: 'Издание «Секрет фирмы» опубликовало рейтинг самых успешных молодых предпринимателей возрастом до 40 лет с российским гражданством. Лидером списка стал основатель «ВКонтакте» и Telegram Павел Дуров.',
photo: {
id: 391449072,
album_id: -2,
owner_id: 1,
photo_75: 'http://cs628523.v...0bb/EhKBPspY4c0.jpg',
photo_130: 'http://cs628523.v...0bc/r85yDlLEX4s.jpg',
photo_604: 'http://cs628523.v...0bd/0vJL28E-p_M.jpg',
photo_807: 'http://cs628523.v...0be/cOyGd6iGxO8.jpg',
width: 722,
height: 337,
text: '',
date: 1448431412
},
is_external: 1
}
}],
post_source: {
type: 'vk'
}
}],
post_source: {
type: 'vk'
},
comments: {
count: 0,
can_post: 1
},
likes: {
count: 17,
user_likes: 0,
can_like: 1,
can_publish: 1
},
reposts: {
count: 2,
user_reposted: 0
}
}]

Not the best example, since there is only 1 repost history, but the bottom line is that
I am interested in the last element of the copy_history array in the returned value, and I will check it for text matching -
r.response[0].copy_history[r.response[0 ].copy_history.length - 1].text == 'my text'
How to find out the size of the array returned in vk api? = I wanted to ask this question first, but it seems to me that r.response[0].copy_history.length - 1 should work, the problem is that r.response[0].copy_history - undefined
It seems logical to me, but this does not work .. and:
alert(r.response[0].copy_history); returns undefined.
Why? and how then to check the repost for compliance with my initial post?

Answer 1

THANK YOU Neoline Neoline
I looked console.log(r.response[0]); and I understood everything, there really is no copy_history there), apparently the documentation on their website is outdated. Thanks again
and for those who are interested, I present the answer -
Object {id: 38085, from_id: -51370128, to_id: -51370128, date: 1448435117, post_type: "copy"…}
attachment: Object
attachments: Array[1]
comments: Object
copy_owner_id: 1
copy_post_date: 1448431475
copy_post_id: 593585
copy_post_type: "post"
copy_text: "Pavel's comment about the article in Sekret Firmy. #durov #paveldurov
The Secret of the Firm publication published a rating of the most successful young entrepreneurs under the age of 40 with Russian citizenship. The leader of the list was the founder of VKontakte and Telegram Pavel Durov.
"The Secret of the Firm" has built a rating by reducing the value of the entrepreneur's share in his business. The leader of the list, 31-year-old Pavel Durov, wholly controls Telegram, which the publication has valued at $1 billion. Durov himself believes that his company is worth about $3-4 billion.
In second place is Ivan Tavrin, 39, CEO of MegaFon and co-owner YuTV Holding, in which he owns 50%. His stake was valued at $400 million.
Brothers Semyon and Efim Voinov (both 33 years old) took the third and fourth places, their shares in the game developer Zeptolab are estimated at $250 million. In fifth place is 38-year-old founder of the OneTwoTrip flight search engine Pyotr Kutis ($130 million)."
date: 1448435117
from_id: -51370128
id: 38085
likes: Object
post_type: "copy"
reposts: Object
text: "Is it possible to give a market value for something that is not for sale?"
to_id: -51370128
__proto__: Object
did not reveal everything, you can see for yourself

Answer 2

<?
//код
echo response[0].copy_history[0].text;
?>

<script>
//код
alert(response[0].copy_history[0].text);
</script>