Elena Authoring

Elena Authoring — Critical Rules

Full reference: https://getelena.github.io/elena/llms-full.txt Page index: https://getelena.github.io/elena/llms.txt

Component types

Three types — the type determines whether render() is present:

• Primitive: owns its DOM, MUST have render() returning an html tagged template. Elena calls replaceChildren() on every render.
• Composite: wraps composed children, must NOT have render(). Never touches light DOM children.
• Declarative: hybrid using <template shadowrootmode="open"> in the HTML markup. No render().

Props

• Props must be declared in BOTH static props AND as class field defaults. Neither alone is sufficient.
• The type is inferred from the default value: false → Boolean, 0 → Number, [] → Array, {} → Object, "..." → String.
• "text" is a reserved built-in prop. Never include it in static props — Elena throws: "text" is reserved.
• Use { name: "icon", reflect: false } in static props to suppress attribute reflection for a specific prop.
• Annotate every prop with JSDoc @property and @type on the class field.

Events

• static events tells Elena which events to manage from the inner element.
• Bubbling events (like click, change, input) pass through to the host naturally with all their original properties intact.
• Non-bubbling events (like focus and blur) are forwarded to the host as plain Event instances.
• Never override handleEvent() on a component that uses static events — Elena uses it internally for delegation.
• Dispatch custom events with new CustomEvent("my-event", { bubbles: true, composed: true, detail: { value } }).

Templates

• render() must return an html tagged template literal. Import html and nothing from @elenajs/core.
• Use nothing (not "" or false) in conditional expressions to avoid template shape changes.
• Nested html fragments pass through without double-escaping. Plain string values are auto-escaped (XSS-safe).
• this.text captures the element's textContent on connect. Use it in render() for text content.
• unsafeHTML(str) bypasses escaping — only use for trusted, sanitized content.
• html does NOT block JavaScript URIs. Always validate URLs before interpolating into href or other URL attributes: const safeUrl = /^https?:\/\//.test(url) ? url : "#";

Lifecycle

• willUpdate() — runs before every render. Must NOT call super. Use for derived state.
• firstUpdated() — runs once after the first render. this.element is available here.
• updated() — runs after every render, including the first. Runs after firstUpdated().
• this.element is available in render(), lifecycle methods, and custom methods. It is resolved after the first render completes.
• requestUpdate() — manually schedule a re-render when Elena cannot detect a change (e.g. mutating an array in place).
• updateComplete — Promise that resolves after the current render microtask finishes. Use to await DOM updates: await element.updateComplete.
• All lifecycle methods except willUpdate() should call super.

Mixins

• Apply mixins after Elena(): class Foo extends Draggable(Elena(HTMLElement)) {}.
• Mixins that override lifecycle methods must call super (except willUpdate()).
• Props introduced by a mixin must be listed in static props on the final concrete class.

Registration

• Always call ClassName.define() after the class body, not inside it.
• define() is a no-op in non-browser environments (SSR-safe).

Framework compatibility

• Never render a framework component inside a Primitive Component. Elena calls replaceChildren() on render, destroying the framework tree.
• For dynamic text content in frameworks, use the text property: <elena-button text={label} />. Children won't update after hydration.
• Avoid letting the framework and Elena both mutate the same attribute — the framework's reconciler will win on next render.
• Angular: Text children are inserted after connectedCallback fires, so Elena has already replaced the host's inner DOM by then. Always use text as a property binding, never as a child node: <elena-button [text]="label"></elena-button>.
• React 17: Does not pass Array or Object type props or event handlers to custom elements correctly. Use React 18+ or pass all props as string attributes.

Source: getelena/elena — distributed by TomeVault.