@zeus-js/signal

The public reactivity package exposes the same small contract as @zeus-js/zeus.

import {
  createSignal,
  createMemo,
  createEffect,
  createRoot,
  onCleanup,
  batch,
} from '@zeus-js/signal'

Export	Description
createSignal	Create a shallow getter/setter signal
createMemo	Create a cached derived getter
createEffect	Run a dependency-tracked side effect
createRoot	Own effects and cleanup under an explicit root
onCleanup	Register effect or owner cleanup
batch	Flush dependent effects after grouped mutations

createSignal

const [count, setCount] = createSignal(0)

count() // 0
setCount(1)
setCount(previous => previous + 1)

Signals are shallow. Replace objects and arrays explicitly:

const [todos, setTodos] = createSignal<Todo[]>([])

setTodos(current => [...current, nextTodo])

createMemo

const doubled = createMemo(() => count() * 2)

The computation is lazy and cached until one of its dependencies changes.

createEffect and onCleanup

createEffect(() => {
  const handler = () => console.log(count())
  window.addEventListener('click', handler)

  onCleanup(() => {
    window.removeEventListener('click', handler)
  })
})

Cleanup runs before the effect reruns and when its owner is disposed.

createRoot

const dispose = createRoot(dispose => {
  createEffect(() => console.log(count()))
  return dispose
})

dispose()

batch

batch(() => {
  setCount(1)
  setCount(2)
})

Dependent effects flush once with the final value.

Runtime diagnostics

@zeus-js/signal/diagnostics provides opt-in counters for performance tests and component diagnostics. It is separate from the application entry so normal application code does not expand the public @zeus-js/signal surface.

import { createRuntimeDiagnosticsSession } from '@zeus-js/signal/diagnostics'

const diagnostics = createRuntimeDiagnosticsSession()

const dispose = diagnostics.run(() =>
  createRoot(dispose => {
    createEffect(() => {})
    return dispose
  }),
)

dispose()
console.log(diagnostics.snapshot())
diagnostics.dispose()

The snapshot counts effects, scopes, refs, memos and Proxy cache misses created under the session. Only effects and scopes have deterministic disposal counts. Proxy, ref and memo lifetime remains controlled by garbage collection, so the API does not report synthetic disposal values for them. allocationsCreated and allocationsDisposed are aggregates of these runtime-owned categories, not a measurement of all JavaScript heap allocations.

run() is deliberately synchronous: it returns the callback result and rejects Promise-returning callbacks at the type boundary. Effects and scopes created during that callback retain their session attribution for later synchronous runs, but unrelated asynchronous continuations are not implicitly captured.

Internal engine

@zeus-js/signal/internal is reserved for Zeus packages. It is not an application interface and has no compatibility guarantees.