.js works in chrome and firefox but not IE

Question

When testing my website in IE11, some parts of it do not work, and I believe that the problem is with my custom.js file, since all the problems are related to this js. However, the page works fine in Chrome and Firefox.

I upload a .js file called "custom.js" to the footer of my page along with other plugins with plugins (jquery and bootstrap are loaded to the head) as follows:

<!-- JS Implementing Plugins -->
<script type="text/javascript" src="/js/back-to-top.js"></script>
<script type="text/javascript" src="/js/smoothScroll.js"></script>
<script type="text/javascript" src="/js/jquery.parallax.js"></script>
<script type="text/javascript" src="/js/masterslider.min.js"></script>
<script type="text/javascript" src="/js/jquery.easing.min.js"></script>
<script type="text/javascript" src="/js/owl.carousel.min.js"></script>
<script type="text/javascript" src="/js/jquery.cubeportfolio.min.js"></script>

<!-- JS Customization -->
<script type="text/javascript" src="/js/custom.js"></script>

<!-- JS Page Level -->
<script type="text/javascript" src="/js/app.js"></script>
<script type="text/javascript" src="/js/owl-carousel.js"></script>
<script type="text/javascript" src="/js/master-slider-fw.js"></script>
<script type="text/javascript" src="/js/jquery.owl-filter.js"></script>
<script type="text/javascript" src="/js/material.min.js"></script>

<script type="text/javascript">
    jQuery(document).ready(function() {
        App.init();
        App.initCounter();
        App.initParallaxBg();
        FancyBox.initFancybox();
        MSfullWidth.initMSfullWidth();
        OwlCarousel.initOwlEvent();
        OwlCarousel.initOwlSingle();
        OwlCarousel.initOwlTwo();
        OwlCarousel.initOwlAbout();

    });
    $(document).ready(function(){
        $('.owl-carousel').owlCarousel({
            nav:true,
            loop:true
        });
    });

</script>

<!--[if lt IE 9]>
<script src="/plugins/respond.js"></script>
<script src="/plugins/html5shiv.js"></script>
<script src="/plugins/placeholder-IE-fixes.js"></script>

The contents of the custom.js file:

$(".helpform-container:not(.displayblock)").hide();
    $(".helpform")
        .on('mouseover focus', function(e) {
            $(this).addClass("link-div-hover")
        })
        .on('mouseout blur', function(e) {
            $(this).removeClass("link-div-hover")
        })
        .on('touchstart', function(e) {
            $(this).addClass("link-div-hover")
        })
        .on('touchend', function(e) {
            $(this).removeClass("link-div-hover")
        })
        .on('click', function(e) {
            $(this).toggleClass("active");
            e.preventDefault();

            if ($(".helpform-container").is(":hidden")) {
                $(".helpform-container").slideDown(400).addClass("displayed");
                analyticsevent('How can we help form', 'open');
            } else {
                $(".helpform-container").slideUp(400).removeClass("displayed");
                $("#sticky-wrapper").css("height","auto");
                analyticsevent('How can we help form', 'closed');
            }

            if (sitewidth < 1024) {
                $('html,body').animate({ scrollTop: $("#howcanwehelp").offset().top - 60 }, 250);
            } else {
                $('html,body').delay(500).animate({ 
                    scrollTop: $("#howcanwehelp").offset().top 
                }, 400);
            }
        })

    //FORM METRICS
    if ($('.formsent').length){
         analyticsevent('Contact form completed', 'consultation/quote/info/media');
    }

//Homepage news articles

var divs = $(".owl-news > .news-v2");
let array = [
  { length: 1, num: 4 },
  { length: 2, num: 3 },
  { length: 2, num: 3 },
  { length: 3, num: 2 }  
];

let i = 0;


for (let item of array) {
  divs.slice(i, i+item.length).wrapAll(`<div id='news-${item.num}' class='col-md-${item.num}'></div>`);
  i += item.length;
}

$("#news-4").before("<div class='col-md-4'><h3 id='title_featured'>Featured News</h3></div><div class='col-md-8'><h3 id='title_latest'>Latest News</h3></div>");

Answer 1

Problem: Internet Explorer 11, released in 2013, does not launch ECMAScript 2015 (for obvious reason).

: Babel ()

, . .

<!-- Load the in-browser babel compiler.  Make sure page encoding is UTF-8. -->
<script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
<!-- Set script type to text/babel for on-the-fly conversion and execution -->
<script type="text/babel" src="custom.js"></script>
<!-- Babel need to read the script through ajax, same origin policy applies. -->

---

: ES5

custom.js ES5 , - ES6/7/8 + :

var divs = $(".owl-news > .news-v2"),
   array = [
      { length: 1, num: 4 },
      { length: 2, num: 3 },
      { length: 2, num: 3 },
      { length: 3, num: 2 }  
   ],
   i = 0;

array.forEach( function( item ) {
  divs.slice(i, i+item.length).wrapAll( "<div id='news-"+item.num+"' class='col-md-"+item.num+"'></div>" );
  i += item.length;
} );

---

: Script

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---

: IE 11

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Answer 2

javascript let, IE11. ...

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- :

debugger;
$(".helpform-container:not(.displayblock)").hide();
...
$("#news-4").before("<div class='col-md-4'><h3 id='title_featured'>Featured News</h3></div><div class='col-md-8'><h3 id='title_latest'>Latest News</h3></div>");