webpack-pug js function is not a function

Im new to webpack and pug . Working on a small task and

• I wrote a function dropDown() in drop.js exported it in index.js file,
• tried to put it in PUG file
  but:
• console writing wether ‘function is not defined’ or f’unction is not a function’.
• Please could anyone help me to solve that problem with correct defining js function

here is the link to my webpack.config
enter link description here

here is my json file
enter link description here

in PUG file i use function like this:

 .searchbox-drop
    button(href="#" data-dropdown='drop1' onclick='dropDown()' aria-controls='drop1' aria-expanded=false class='dropbtn') Вce
      +image('triangle','searchbox-drop__icon' )  

in index.js

import $ from "jquery";
import 'bootstrap';
import './styles/index.scss';
import {dropDown} from './drop.js';





window.dropDown = dropDown();

in drop.js

export function dropDown(){ 
function show() {
  document.getElementById('myDropdown').classList.toggle('show');
}

//close dropdown id the user cliks outside of it
window.onclick = function(e){
if(!e.target.matches('.dropbtn')){
    var myDropdown = document.getElementById('myDropdown');
    if(myDropdown.classList.contains('show')){
      myDropdown.classList.remove('show');
    }
  }
}

}