static methods/properties live on the class, not instances (User.create()) — good for factories and constants. Fields prefixed with # (#secret) are genuinely private: inaccessible outside the class, unlike the old underscore convention. This finally gives JS real encapsulation.
<!doctype html><html><head><meta charset="utf-8"></head>
<body style="background:#06040d;color:#e6e0ff;font-family:monospace;padding:20px"><pre id="o"></pre>
<script>class Counter{ #n=0; static make(){ return new Counter(); } inc(){ return ++this.#n; } }
const c=Counter.make();
document.getElementById('o').textContent=[c.inc(),c.inc()].join(' ');</script></body></html>