JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/choices.js/3.0.4/choices.js" integrity="sha256-dvGgc5pCu9HxC5R5pdTBm3FLizdgDUOA5iu7TOlVtEc=" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/choices.js/3.0.4/styles/css/choices.css" integrity="sha256-JDRgPmLPsdG/wIG2fjAJxA/KhUJU4+7HblQl5UfgR0c=" crossorigin="anonymous" />


<select>
<option>1</option>
<option selected>2</option>
<option>3</option>
<option>4</option>
<option>5</option>
<option>6</option>
<option>7</option>
</select>

JavaScript

let holidaySelectDay


function uselessFunction() { 
  return new Promise(resolve => {
      copyDiv()
      resolve(0);
  });
}

async function f1() {
  var x = await uselessFunction();
  choicesInit('select', {searchEnabled: false, shouldSort: false, itemSelectText: ''});
}

f1();




/* -------------------- */
function copyDiv() {
  holidaySelectDay = document.querySelector("select");
  console.log(holidaySelectDay);
}

function choicesInit(select, param) {
  const elements = Array.from(document.querySelectorAll(`${select}`))
  // Если есть атрибут 'data-choice' - значит селект обрабатывался библиотекой - отбасываем его
  const item = elements.filter(function (elements) {
    if (!elements.getAttribute('data-choice')) { return elements }
  });
  const instances = item.map((element) => {
    return new Choices(element, param)
  });
}