.
$ npm install mf-parser
const parseToHtml = require('mf-parser').parseToHtml;
let html = parseToHtml('Et3N . 2HCl);
You may also be interested to parse first the MF and then retrieve display representation
const MFParser = require('mf-parser');
let parsed = MFParser.parse('Et3N . 2HCl');
let displayed = MFParser.toDisplay(parsed);
// displayed could be used to ocreate a custom renderer
console.log(displayed);
Unsaturation is based on Pretsch
http://pubs.acs.org/doi/pdf/10.1021/ci000135o