[WA]

Perfect candidate for a nice, simple, self-contained web component / custom element. Instead of:

    <div id="json-tree"></div>
    ...
    const container = document.getElementById('json-tree');
    container.innerHTML = generateJSONTree(jsonData);

You'd have this:

    <json-tree id="json-tree"></json-tree>
    ...
    const container = document.getElementById('json-tree');
    container.jsonTree = jsonData;

Attributes not necessary, simply pass the json data as a prop. Granted, the difference isn't that big, but this is where web components shine.