Plain Javascript Code That Does What QuerySelector() And QuerySelectorAll() Does, Include Shadowroots

I am trying to write a method that takes in two params: one of the parentNode of the current element where many childNodes with shadowroots within it, the second param being the id

Solution 1:

You must create a parser that will check recursively the DOM :

For each node :

1. If there's a Shadow DOM (shadowRoot not null), parse the Shadow tree.
2. Or else parse the children DOM tree.

If you use <slot> you'll have look for distributed nodes too, but it's not asked in your question...