# useIsMounted

> A stable getter for whether the component is still mounted.

- Category: Effects
- Package: `hookli` (install with `npm i hookli`)
- Docs: https://hookli.vercel.app/docs/use-is-mounted

## Signature

```ts
useIsMounted(): () => boolean
```

## Returns

- `isMounted`: `() => boolean` — A stable getter that returns true while mounted and false after unmount. Call it inside async callbacks before setting state; its identity never changes, so it is safe to omit from dependency arrays.

## Usage

```tsx
import { useIsMounted } from "hookli";

export function Demo() {
  const isMounted = useIsMounted();

  async function load() {
    const data = await fetchData();
    if (isMounted()) setData(data);
  }

  return <button onClick={load}>Load</button>;
}
```

## Source

`src/hooks/use-is-mounted/use-is-mounted.ts`

```ts
import { useCallback, useEffect, useRef } from "react";

export const useIsMounted = () => {
  const isMounted = useRef(false);

  useEffect(() => {
    isMounted.current = true;
    return () => {
      isMounted.current = false;
    };
  }, []);

  return useCallback(() => isMounted.current, []);
};
```