https://github.com/joewalnes/filtrex https://github.com/TomFrost/Jexl https://github.com/aviaryan/BigEval.js https://www.npmjs.com/package/@code-dot-org/js-interpreter
https://github.com/ajaxorg/ace (generic code editor, how to create custom rule: https://medium.com/@jackub/writing-custom-ace-editor-mode-5a7aa83dbe50)