Secondary primitives

createReaction

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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