Userscript: Dvach (2ch.hk) Image Options (Reverse + DDL)

// ==UserScript==
// @name         Dvach Image Options
// @version      0.2
// @description  Adds direct download button and reverse image search options
// @author       ему
// @match        https://2ch.hk/*/res/*
// @require      https://code.jquery.com/jquery-3.2.1.min.js
// @resource     fa_CSS https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css
// @grant        GM_addStyle
// @grant        GM_getResourceText
// ==/UserScript==

this.$ = this.jQuery = jQuery.noConflict(true);

GM_addStyle(GM_getResourceText("fa_CSS"));

GM_addStyle(".image-reverse { text-decoration:none;margin-left:4px;color:#666666;font-size:10px; } .image-reverse:hover { text-decoration: underline; } .image-direct-download { text-decoration:none;margin-left:4px;font-size:14px; }");

function getReverseImageSearchOptions(url)
{
    var options = {
        'google': 'https://www.google.com/searchbyimage?image_url=' + url + '&safe=off',
        'yandex': 'https://www.yandex.com/images/search?rpt=imageview&img_url=' + url,
        'iqdb': 'https://iqdb.org/?url=' + url
    };

    return options;
}

var re = new RegExp('(mp4|webm)');

function onElementHeightChange(elm, callback)
{
    var lastHeight = elm.clientHeight, newHeight;
    (function run()
    {
        newHeight = elm.clientHeight;
        if(lastHeight != newHeight)
            callback();
        lastHeight = newHeight;

        if(elm.onElementHeightChangeTimer)
            clearTimeout(elm.onElementHeightChangeTimer);

        elm.onElementHeightChangeTimer = setTimeout(run, 1000);
    })();
}

function applyOptions()
{

  $(".file-attr").each(function(index)
  {

    if($(this).find('.image-options').length > 0)
    {
        return;
    }

    var file_url = $(this).find('a');

    if(file_url != undefined)
    {
        $reverse_options = getReverseImageSearchOptions(document.location.origin + file_url.attr('href'));

        if (re.test(file_url.attr('href'))) {
          $preview = $(this).parent().find('.preview');

          if($preview.length > 0)
          {
            if($preview.attr('src') != undefined)
            {
              $reverse_options = getReverseImageSearchOptions(document.location.origin + $preview.attr('src'));
            }
          }
        }

        var first_c = $(this).find(">:first-child");

        var direct_download = '<a class="fa fa-download image-direct-download" href="' + file_url.attr('href')  + '" download="' + file_url.attr('title') + '"></a>';
        var r_google = '<a target="_blank" href="' + $reverse_options['google']  + '" class="image-reverse">google</a>';
        var r_yandex = '<a target="_blank" href="' + $reverse_options['yandex']  + '" class="image-reverse">yandex</a>';

        first_c.after('<div class="image-options" style="display:inline-block;">' + direct_download + r_google + r_yandex + '</div>');

    }
  });
}

$(document).ready(function()
{

  onElementHeightChange(document.body, function(){
    applyOptions();
  });

  applyOptions();

});