onMount & onCleanup in SolidJS

From the SolidJS cheat sheet · Lifecycle · verified Jul 2026

onMount & onCleanup

Run code after the component mounts or when it unmounts.

typescript

// Quick Reference
import { onMount, onCleanup } from "solid-js";

onMount(() => {
  console.log("Component mounted");
});

onCleanup(() => {
  console.log("Component unmounted");
});

💡 onMount runs once after the component is first rendered to the DOM

⚡ onCleanup works in both components and effects — cleans up between re-runs too

📌 Since components run only once, you can set up intervals directly in the function body

🟢 onMount is equivalent to createEffect that runs only on first execution

lifecyclemountcleanup

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