Is there anyway to always execute a function whenever localStorage value change in Svelte?

I'm using a bought template in my Laravel Inertia Svelte app. This template has 2 "shapes", Vertical (Sidebar Menus) and Horizontal (Navbar Menus).

My app right now has 3 components: Sidebar, Navbar, and Footer. They are included inside the layout. The layout looks something like this:

<main class="main" id="top">
    <TheSidebar />
    <div class="content">
        <slot />
        <TheFooter />
    </div>
</main>
<ThemeCustomizer />

What I want to do is basically change the layout when the value inside localStorage change. I have a button inside ThemeCustomizer component that change the localStorage value. For example, if I click Vertical button, then the value inside localStorage changes to 'vertical', and it changes to 'horizontal' if I click Horizontal button.

I tried to do the following:

{#if localStorage.getItem('phoenixTheme') === 'vertical'}
    <main class="main" id="top">
        <TheSidebar />
        <div class="content">
            <slot />
            <TheFooter />
        </div>
    </main>
{:else}
    <main class="main" id="top">
        <TheNavbar />
        <div class="content">
            <slot />
            <TheFooter />
        </div>
    </main>
{/if}
<ThemeCustomizer />

However it doesn't work. It does work when I fully reload the page, but it doesn't work when I just click the button and change the value inside localStorage. I assume this is because the if else checking is just done once.

Is there a way to basically always trigger the if else function when the localStorage value change? Thank you.

You can wrap the storage in a store and subscribe to the storage event and update the store value on change. If you then use the store via $store in the markup it will update automatically.

There are probably full implementations of this around and there are several questions about local/session storage when used with Svelte stores.

(If you do not need updates across multiple tabs, you do not need to listen for the event. Having the store reactivity will be enough if all access is through said store.)