Method createEffect

src/core/runtime/reactivity.js:646–666

* Create a reactive effect with automatic dependency tracking. * @param {() => any} expression - The watched expression * @param {(value: any) => void} handler - Called when the value changes * @param {Object} [options] * @param {Element} [options.element] - Auto-stop when elemen

(expression, handler, options)

     * @returns {() => void} Stop function
     */
    createEffect(expression, handler, options) {
        var effect = new Effect(
            expression,
            handler,
            (options && options.element) || null,
            this
        );

        effect.initialize();

        // Track effect by element for cleanup
        if (effect.element) {
            var data = effect.element._hyperscript ??= {};
            data.effects ??= new Set();
            data.effects.add(effect);
        }

        return function () {
            effect.stop();
        };
    }

    /** Stop all reactive effects owned by an element. */
    stopElementEffects(element) {