How to add images in the options of a tag using vanilla js?

var langArray = [];
$('.vodiapicker option').each(function(){
  var img = $(this).attr("data-thumbnail");
  var text = this.innerText;
  var value = $(this).val();
  var item = '<li><img src="'+ img +'" alt="" value="'+value+'"/><span>'+ text +'</span></li>';
  langArray.push(item);
})

$('#a').html(langArray);


$('.btn-select').html(langArray[0]);
$('.btn-select').attr('value', 'en');


$('#a li').click(function(){
   var img = $(this).find('img').attr("src");
   var value = $(this).find('img').attr('value');
   var text = this.innerText;
   var item = '<li><img src="'+ img +'" alt="" /><span>'+ text +'</span></li>';
  $('.btn-select').html(item);
  $('.btn-select').attr('value', value);
  $(".b").toggle();

});

$(".btn-select").click(function(){
        $(".b").toggle();
    });


var sessionLang = localStorage.getItem('lang');
if (sessionLang){

  var langIndex = langArray.indexOf(sessionLang);
  $('.btn-select').html(langArray[langIndex]);
  $('.btn-select').attr('value', sessionLang);
} else {
   var langIndex = langArray.indexOf('ch');
  console.log(langIndex);
  $('.btn-select').html(langArray[langIndex]);
}

.vodiapicker{
  display: none; 
}

#a{
  padding-left: 0px;
}

#a img, .btn-select img{
  width: 12px;
  
}

#a li{
  list-style: none;
  padding-top: 5px;
  padding-bottom: 5px;
}

#a li:hover{
 background-color: #F4F3F3;
}

#a li img{
  margin: 5px;
}

#a li span, .btn-select li span{
  margin-left: 30px;
}

/* item list */

.b{
  display: none;
  width: 100%;
  max-width: 350px;
  box-shadow: 0 6px 12px rgba(0,0,0,.175);
  border: 1px solid rgba(0,0,0,.15);
  border-radius: 5px;
  
}

.open{
  display: show !important;
}

.btn-select{
  margin-top: 10px;
  width: 100%;
  max-width: 350px;
  height: 34px;
  border-radius: 5px;
  background-color: #fff;
  border: 1px solid #ccc;
 
}
.btn-select li{
  list-style: none;
  float: left;
  padding-bottom: 0px;
}

.btn-select:hover li{
  margin-left: 0px;
}

.btn-select:hover{
  background-color: #F4F3F3;
  border: 1px solid transparent;
  box-shadow: inset 0 0px 0px 1px #ccc;
  
  
}

.btn-select:focus{
   outline:none;
}

.lang-select{
  margin-left: 50px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script><select class="vodiapicker"><option value="en" class="test" data-thumbnail="https://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/LetterA.svg/2000px-LetterA.svg.png">English</option><option value="au" data-thumbnail="https://upload.wikimedia.org/wikipedia/commons/thumb/f/fb/NYCS-bull-trans-B.svg/480px-NYCS-bull-trans-B.svg.png">Engllish (AU)</option><option value="uk" data-thumbnail="https://glot.io/static/img/c.svg?etag=ZaoLBh_p">Chinese (Simplified)</option><option value="cn" data-thumbnail="https://upload.wikimedia.org/wikipedia/commons/thumb/3/39/NYCS-bull-trans-D.svg/2000px-NYCS-bull-trans-D.svg.png">German</option><option value="de" data-thumbnail="https://upload.wikimedia.org/wikipedia/commons/thumb/0/04/MO-supp-E.svg/600px-MO-supp-E.svg.png">Danish</option><option value="dk" data-thumbnail="https://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/F_icon.svg/267px-F_icon.svg.png">French</option><option value="fr" data-thumbnail="https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Google_%22G%22_Logo.svg/2000px-Google_%22G%22_Logo.svg.png">Greek</option><option value="gr" data-thumbnail="https://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/4H_Emblem.svg/1000px-4H_Emblem.svg.png">Italian</option></select><div class="lang-select"><button class="btn-select" value=""></button><div class="b"><ul id="a"></ul></div></div>