You can overwrite the prepareStackTrace property of the Error object by String prototype's functions and invoke them without parentheses. Then by overwriting the Error and Array prototype it is possible to control the arguments. Combining this behavior, together with some JSFuck-inspired tricks, it is possible to generate arbitrary JavaScript strings and run arbitrary JavaScript with only letters + - = and ,

I built penciled, a small MIT library for persistent text highlights and notes in the browser. It uses the CSS Custom Highlight API instead of wrapping ranges in <span>s, so the DOM stays intact and layout/selection quirks are milder. Anchoring tries to survive edits when you come back to the page.

npm: penciled
GitHub: https://github.com/marcellosso/penciled

There's also a companion browser extension (same engine) if you want highlights on arbitrary sites, happy to answer questions about the API or the anchoring approach.