@nexa/reactivity

No Virtual DOM — signals that notify whoever reads them, directly. For writing an island by hand.

state() — Signal

import { state } from "@nexa/reactivity";

const count = state(0);
count.value = 1; // dispara efectos suscriptos

.value reads and subscribes; .peek() reads without subscribing. Writing .value fires the effects that read it, batched by microtask.

computed()

import { computed } from "@nexa/reactivity";

const doubled = computed(() => count.value * 2);
doubled.value; // sin setter

A ReadonlySignal that recalculates on its own. Chaining computeds works, at a real cost: each hop is one more microtask round-trip.

effect()

import { effect } from "@nexa/reactivity";

const stop = effect(() => {
    console.log(count.value);
});
stop();

Runs right away, and again every time something it read changes. Returns a function to turn it off.

watch()

import { watch } from "@nexa/reactivity";

watch(
    () => count.value,
    (nuevo, viejo) => console.log(nuevo, viejo),
);

Like effect, but does NOT run when created — only on later changes. Receives the new and the old value.

bindText()

import { bindText } from "@nexa/reactivity";

bindText(node, () => count.value);

What the compiler automatically generates for {data.x} in a page's body — not something you'd normally write by hand.

mountComponent() — islands only

import { mountComponent, type Component } from "@nexa/reactivity";

const List: Component<{ labels: string[] }> = (el, props, ctx) => {
    for (const label of props.labels) {
        const li = document.createElement("li");
        el.appendChild(li);
        ctx.mount(Item, li, { label });
    }
};

Doesn't apply to Nexa Core pages. Component<P>, typed props, and chained cleanup — no Virtual DOM.