{#each foo as bar}
	<select on:change='handler(bar)'>
		<option>a</option>
		<option>b</option>
	</select>
{/each}

<script>
	export default {
		data: () => ({ foo: [ 1, 2 ], log: [] }),
		methods: {
			handler ( bar ) {
				let { log } = this.get();
				log.push( bar );
				this.set( { log } );
			}
		}
	}
</script>