title: What features are supported by CouchDB javascript engine
body: <p>I want to make a <code>validate_doc_update</code>. What features are supported for this function by CouchDB? Can I use <code>Array.find</code>, <code>Array.map</code>, <code>Object.keys</code> and other functions like those? If latest version supports those features, which CouchDB version should I target to make sure my validation will work seamlessly on every system - I would retrieve CouchDB version and make it's above said version.</p>