Finding if your contenteditable is part of a range across shadow dom.

contenteditable.js

        const selection = document.getSelection()

        if (!selection) { return }

        let hasNode = false

        if (typeof selection.getComposedRanges === "function") {
            const staticRange = selection.getComposedRanges(this.contentEditableElement.getRootNode())[0]
            if (!staticRange) { return }

            range = selection.setBaseAndExtent(
                staticRange.startContainer,
                staticRange.startOffset,
                staticRange.endContainer,
                staticRange.endOffset
            )

            hasNode = selection.containsNode(this.contentEditableElement)
        } else {
            range = selection.getRangeAt(0)
            hasNode = range.intersectsNode(this.contentEditableElement)
        }