svelte/test/runtime/samples/select-change-handler/main.html

<select bind:value="selected" on:change="updateLastChangedTo(selected)">
	{#each options as option}
		<option value="{option.id}">{option.id}</option>
	{/each}
</select>

<script>
	export default {
		methods: {
			updateLastChangedTo(result) {
				this.set({ lastChangedTo: result });
			}
		}
	};
</script>