Unable to download Unity Personal in IE11

Apologies if this is in the wrong place, I couldn't find a thread for the main website.
What happened when trying to download Unity in Internet Explorer 11 (as well as Edge 14) I got the error "SCRIPT438: Object doesn't support property or method 'forEach' (306,9)".
Allegedly IE 9 and above should support this method but it does not for some reason. The issue is that when I click the "By clicking, I confirm that I am eligible[...]" the download button remains disabled.
I did manage to produce some code that is supported by all versions of all browsers. The code is on pastebin as well as below.

Code (JavaScript):

1.     Element.prototype.hasClass = function(classname)
2.     {
3.         return (this.className && new RegExp("(^|\\s)" + classname + "(\\s|$)").test(this.className)) || false;
4.     };
5.     Element.prototype.removeClass = function(classname) {
6.         var re = new RegExp("\\b" + classname + " \\b|\\b " + classname + "\\b|\\b" + classname + "\\b");
7.         if (this.hasClass(classname) || classname == undefined)
8.         {
9.             this.className = this.className.replace(re, "");
10.             return this;
11.         }
12.         return this;
13.     };
14.     Element.prototype.addClass = function(classname) {
15.         if (this.hasClass(classname) || classname == undefined)
16.             return this;
17.        
18.         this.className += (this.className.length <= 0 ? "" : " ") + classname;
19.         return this;
20.     };
21.  
22.     var checkbox = document.querySelector('#personal-checkbox');
23.     var downloadBtns = document.querySelectorAll('.download-btn');
24.     if (checkbox.checked)
25.     {
26.         checkbox.checked = false;
27.     }
28.     if (checkbox)
29.     {
30.         checkbox.onclick = function()
31.         {
32.             if (!checkbox.checked)
33.             {
34.                 for (var i = 0; i < downloadBtns.length; i++)
35.                 {
36.                     downloadBtns[i].addClass("download-checkbox-disable");
37.                 }
38.             }
39.             else
40.             {
41.                 for (var i = 0; i < downloadBtns.length; i++)
42.                 {
43.                     downloadBtns[i].removeClass("download-checkbox-disable");
44.                 }
45.             }
46.         };
47.     }