convert CompareAutocomplete from class definition into simple function call, remove global export

app/assets/javascripts/compare_autocomplete.js

 /* eslint-disable func-names, space-before-function-paren, one-var, no-var, one-var-declaration-per-line, object-shorthand, comma-dangle, prefer-arrow-callback, no-else-return, newline-per-chained-call, wrap-iife, max-len */
 
-window.CompareAutocomplete = (function() {
-  function CompareAutocomplete() {
-    this.initDropdown();
-  }
-
-  CompareAutocomplete.prototype.initDropdown = function() {
-    return $('.js-compare-dropdown').each(function() {
+export default function initCompareAutocomplete() {
+  $('.js-compare-dropdown').each(() => {
     var $dropdown, selected;
     $dropdown = $(this);
     selected = $dropdown.data('selected');
@@ -62,7 +57,4 @@ window.CompareAutocomplete = (function() {
       }
     });
   });
-  };
-
-  return CompareAutocomplete;
-})();
+}

app/assets/javascripts/dispatcher.js

@@ -23,7 +23,7 @@ import Project from './project';
 import projectAvatar from './project_avatar';
 /* global MergeRequest */
 import Compare from './compare';
-/* global CompareAutocomplete */
+import initCompareAutocomplete from './compare_autocomplete';
 /* global ProjectFindFile */
 import ProjectNew from './project_new';
 import projectImport from './project_import';
@@ -617,7 +617,7 @@ import ProjectVariables from './project_variables';
           projectAvatar();
           switch (path[1]) {
             case 'compare':
-              new CompareAutocomplete();
+              initCompareAutocomplete();
               break;
             case 'edit':
               shortcut_handler = new ShortcutsNavigation();

app/assets/javascripts/main.js

@@ -40,7 +40,6 @@ import './admin';
 import './aside';
 import loadAwardsHandler from './awards_handler';
 import bp from './breakpoints';
-import './compare_autocomplete';
 import './confirm_danger_modal';
 import Flash, { removeFlashClickListener } from './flash';
 import './gl_dropdown';