Broken script starting from version 18.3

[Joi]

I have a script for previewing topics from a recent or unread topic page.
As of version 1.18.3 of NodeBB, the script does not work.
Can you help?
This is the script:

(function() {
    'use strict';
    function onhover() {
        /* globals require, $, socket, app */
        var self = $(this);
        if (!self.data('preview-loaded')) {
            socket.emit('topics.loadMore', {
                tid: self.data('my-tid'),
                after: 0,
                count: 1,
                direction: 1
            }, (e, d) => {
                self.data('preview-loaded', 1);
                require('translator').translate(e ? '<span style="color:red;">error: </span>' + e.message : d.mainPost.content,
                                                (d) => {
                    if (app.user.uid === 0) {
                        d = d.replace(/\|\|.*\|\|/g,'<a href="https://domain.com/login">You must be logged in to view this link.</a>');
                    } else {
                        d = d.replace(/\|\|/g,'');
                    }
                    $('#preview-' + self.data('my-tid')).children().html(d.replace(/\|\|/g,''));
                });
            }
                       );
        }
        $('#preview-' + self.data('my-tid')).stop(true).delay(500).fadeIn();
    }

    function onunhover() {
        $('#preview-' + $(this).data('my-tid')).stop(true).fadeOut();
    }

    $(window).on('action:topics.loaded', (event, data) => {
        for (let topic of data.topics) {
            let topicElem = $('[data-tid="' + topic.tid + '"]');
            createPreview(topicElem);
        }
    });

    function addTopicTools() {
        let topicelems = $('[component="category/topic"]');
        topicelems.each((i, elem) => {
            createPreview($(elem));
        });
    }

    function createPreview(topicElem) {
        let tid = parseInt(topicElem.attr('data-tid'));
        if (!$('#preview-' + tid).length) {
            topicElem.find('.content').append('<div class="post-preview" id="preview-' + tid + '"><div class="wrap-post-preview">טוען...</div></div>');
            topicElem.find('.post-preview').hover(function(){$(this).stop(true).fadeIn();},function(){$(this).delay(600).fadeOut();});
            topicElem.find('[itemprop="url"]').data('my-tid', tid).hover(
                onhover,
                onunhover
            );
        }
    }

    $(window).on('action:ajaxify.end', addTopicTools);

})();

(The script also exchanges for guests each link to a login page, to encourage registration)
@baris

[Joi]

I was told the problem is in:
topicElem.find
I do not understand this, I just want the code to work again ...
Thank you!

[baris]

What is your nodebb git hash?

On latest versions topics.loadMore doesn't return mainPost anymore.

If you are running latest master update to get these changes https://github.com/NodeBB/NodeBB/commit/906dc5675e5e1e96a7ff693f07f20987cd08c87a.

Then the main post will be the first item in the posts array when you call topics.loadMore. Then you can use d.posts[0].content instead of d.mainPost.content