Vue import causing cannot assign to read only property 'exports' of object error

I am currently migrating a HTML template to Vue. Now I started to import the Javascript files in the main.js file stored inside src.

My file looks like the following:

import Vue from "vue";
import App from "./App.vue";
import router from "./router";

import pageLoader from "./assets/js/global/page-loader";
import tooltips from "./assets/js/global/tooltips";

Vue.use(pageLoader);
Vue.use(tooltips);

Vue.config.productionTip = false;

new Vue({
  router,
  render: (h) => h(App),
}).$mount("#app");

Every Javascript file is located inside the src/js folder

But once I run the application I receive the following error:

Uncaught TypeError: Cannot assign to read only property 'exports' of object '#<Object>'
    at Module.eval (webpack-internal:///./src/assets/js/utils/plugins.js:56)
    at eval (webpack-internal:///./src/assets/js/utils/plugins.js:57)
    at Module../src/assets/js/utils/plugins.js (app.js:1579)
    at __webpack_require__ (app.js:849)
    at fn (app.js:151)
    at eval (webpack-internal:///./src/assets/js/global/tooltips.js:1)
    at Object../src/assets/js/global/tooltips.js (app.js:1556)
    at __webpack_require__ (app.js:849)
    at fn (app.js:151)
    at eval (webpack-internal:///./src/main.js:15)

The whole Projects can be seen on github on the following link: Link to github

What is causing this error? I would appreciate any kind of help to fix my issue.