A component can change its type altogether with <svelte:component>. In this exercise, we want to show RedThing.svelte if the color is red, GreenThing.svelte if it's green, and so on.
We could do this with a sequence of if blocks...
App.svelte
{#if selected.color === 'red'}
<RedThing/>
{:else if selected.color === 'green'}
<GreenThing/>
{:else if selected.color === 'blue'}
<BlueThing/>
{/if}...but it's a little cumbersome. Instead, we can create a single dynamic component:
App.svelte
<select bind:value={selected}>
{#each options as option}
<option value={option}>{option.color}</option>
{/each}
</select>
<svelte:component this={selected.component}/>The this value can be any component constructor, or a falsy value — if it's falsy, no component is rendered.
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<script>
import RedThing from './RedThing.svelte';
import GreenThing from './GreenThing.svelte';
import BlueThing from './BlueThing.svelte';
const options = [
{ color: 'red', component: RedThing }, { color: 'green', component: GreenThing }, { color: 'blue', component: BlueThing }];
let selected = options[0];
</script>
<select bind:value={selected}> {#each options as option} <option value={option}>{option.color}</option> {/each}</select>
{#if selected.color === 'red'}<RedThing />
{:else}<p>TODO others</p>
{/if}