https://travelers.pl/wp-content/plugins/contentation-produkty/js/scripts.js?ver=8156

1// Create Variables
2var allOSB = [];
3var mxh = '';
4
5window.onload = function() {
6  // Set Variables
7  allOSB = document.getElementsByClassName("short-description");
8  
9  if (allOSB.length > 0) {
10    mxh = window.getComputedStyle(allOSB[0]).getPropertyValue('max-height');
11    mxh = parseInt(mxh.replace('px', ''));
12    
13    // Add read-more button to each OSB section
14    for (var i = 0; i < allOSB.length; i++) {
15      var el = document.createElement("button");
16      el.innerHTML = "Więcej";
17      el.setAttribute("type", "button");
18      el.setAttribute("class", "read-more hid");
19      
20      insertAfter(allOSB[i], el);
21    }
22  }
23  var readMoreButtons = document.getElementsByClassName("read-more");
24  for (var i = 0; i < readMoreButtons.length; i++) {
25    readMoreButtons[i].addEventListener("click", function() { 
26      revealThis(this);
27    }, false);
28  }
29  updateReadMore();
30}
31window.onresize = function() {
32  updateReadMore();
33}
34function updateReadMore() {
35  if (allOSB.length > 0) {
36    for (var i = 0; i < allOSB.length; i++) {
37      if (allOSB[i].scrollHeight > mxh) {
38        if (allOSB[i].hasAttribute("style")) {
39          updateHeight(allOSB[i]);
40        }
41        allOSB[i].nextElementSibling.className = "read-more";
42      } else {
43        allOSB[i].nextElementSibling.className = "read-more hid";
44      }
45    }
46  }
47}
48function revealThis(current) {
49  var el = current.previousElementSibling;
50  if (el.hasAttribute("style")) {
51    current.innerHTML = "Więcej";
52    el.removeAttribute("style");
53  } else {
54    updateHeight(el);
55    current.innerHTML = "Mniej";
56  }
57}
58function updateHeight(el) {
59  el.style.maxHeight = el.scrollHeight + "px";
60}
61
62function insertAfter(referenceNode, newNode) {
63    referenceNode.parentNode.insertBefore(newNode, referenceNode.nextSibling);
64}