Reactivity

Introduced in v0.1 (Milestone 1).

@pixelscriptio/tessera/core provides three primitives. A signal is read and written with .value.

import { state, derived, effect } from '@pixelscriptio/tessera/core'

const count = state(0)
const label = derived(() => `Clicked ${count.value} times`)

effect(() => console.log(label.value)) // logs "Clicked 0 times"
count.value++ // logs "Clicked 1 times" in the next microtask

• state(initial) is a writable signal. Setting an identical value (Object.is) does nothing.
• derived(fn) is lazy and memoized. If it recomputes to the same value, nothing downstream re-runs. Keep it pure.
• effect(fn) runs immediately, then again whenever a signal it read changes. Re-runs are batched into one microtask.
• onCleanup(fn) runs before an effect re-runs and when it is disposed. Effects created inside an effect are disposed with it.
• createRoot(fn) makes a scope you dispose yourself; untrack(fn) reads without subscribing; flush() runs pending effects now.

Effects that keep re-triggering each other for 1000 passes throw an error.