Just for clarifying, I want to test in playground this minimal code:

const linkedList = new LinkedList();
linkedList.append('aaa');
linkedList.append('bbb');
console.log(linkedList.reverse().toString());

I got it, but I needed some changes:
-adding "type": "module"," in my package.json
-adding extension .js in my imports
-finally executing: $ node src/playground/playground.js

but must be easier, I think I'm missing something (sure because my lack of knowledge about ES6 modules).
May be it is a good idea to clarify this point at README. TIA