Bootstrap is only a CSS framework it doesn't give you a way to manipulate the DOM for example.
You could in principle do everything with vanilla JS, or jQuery, but I'd recommend you to take some time and learn a modern library to avoid micro managing the DOM.
Vue is super easy and is excellent for beginners. You just need to import Vue with a
<script> tag, write your templates directly in your
index.html and finally write your JS somewhere (either another
<script> or some
.js file). You can of course get it running with Webpack, ES6, the whole enchilada, but it's not needed.