VS Code – don’t see variables when debugging JS

I’m trying to debug a simple program in JS:

var a = [1,2,2,2,3];
        var b = [2];
        function arrayDiff(a, b) {
            console.log(a,b);
            for(var i = 0; i < b.length; i++) {
                if(a.includes(b[i])){
                    a.splice(b[i]);
                    console.log(a,b);
                }
            }
            return a,b;
        }
        
        var array1 = [1,1,2];
        var array2 = [1];
        console.log(arrayDiff(array1,array2));

and see how the variables act. I have a HTML file connected to this, downloaded Debugger for Firefox and created the following launch.json file:

{
// Use IntelliSense to learn about possible attributes.
// Hover to view descriptions of existing attributes.
// For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
"version": "0.2.0",
"configurations": [

    {
        "name": "Launch index.html",
        "type": "firefox",
        "request": "launch",
        "reAttach": true,
        "file": "${workspaceFolder}/index.html"
    },
    {
        "name": "Launch localhost",
        "type": "firefox",
        "request": "launch",
        "reAttach": true,
        "url": "http://localhost/index.html",
        "webRoot": "${workspaceFolder}"
    },
    {
        "name": "Attach",
        "type": "firefox",
        "request": "attach"
    },
    {
        "name": "Launch WebExtension",
        "type": "firefox",
        "request": "launch",
        "reAttach": true,
        "addonPath": "${workspaceFolder}"
    }
]}

However I still cannot see the variables when I put breakpoints and so on… I’ve tried everything from reinstalling the extension, setting up Firefox browser itself with the values recommended in the extension’s readme, localhost, attach, or opening directly the index.html file. Looked through stack overflow and none of the solutions have helped yet…

Running Pop!_OS 22.04 LTS.

Thanks!