Define

define() registers the element; the registered class then carries its own configuration for anyone who needs to inspect it.

define()

define(tag?, options?) registers the element. Both default to the config (tag, definitionOpts) and are passed straight to customElements.define. Defining an already-registered tag logs a warning instead of throwing.

Neutron({ tag, props, ssr: false }) keeps the tag's instances out of a prerender: an element that reads the device or the person mounts in the browser only, and what it holds prerenders as usual. Default true.

Introspection

The defined element class carries its runtime configuration as two static methods. Reach the class through the registry or an instance's constructor:

const Drawer = customElements.get("content-drawer") as typeof NeutronElement;
Drawer.getConfig();                            // { tag, props, events, broadcasts, methods, lifecycles, … }
Drawer.getPropConfig({ attr: "open-stage" });  // { prop: "openStage", attr: "open-stage", type: Number, … }
(el.constructor as typeof NeutronElement).getPropConfig({ prop: "isOpen" });

getConfig() returns the RuntimeConfig built by define() (undefined before it); getPropConfig({ attr }) / getPropConfig({ prop }) return one prop's PropConfig or undefined. Treat both as read-only. A typical use is whitelisting event payloads: keep only detail keys that name a declared, non-private prop before applying them as an effect (see content-drawer).