Secondary Primitives

createReaction

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import { createReaction } from "solid-js"


function createReaction(onInvalidate: () => void): (fn: () => void) => void

Sometimes it is useful to separate tracking from re-execution. This primitive registers a side effect that is run the first time the expression wrapped by the returned tracking function is notified of a change.

const [s, set] = createSignal("start")


const track = createReaction(() => console.log("something"))


// run the reaction next time `s` changes.
track(() => s())


set("end") // "something"


set("final") // no-op since the reaction only runs on the first update, need to call `track` again.
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