svelte/test/runtime/samples/event-handler-custom/main.html

<button on:tap='set({ x: event.x, y: event.y })'>{x}, {y}</button>

<script>
	export default {
		data: () => ({
			x: 0,
			y: 0
		}),

		events: {
			tap ( node, callback ) {
				function clickHandler ( event ) {
					callback({
						x: event.clientX,
						y: event.clientY
					});
				}

				node.addEventListener( 'click', clickHandler, false );

				return {
					destroy () {
						node.addEventListener( 'click', clickHandler, false );
					}
				};
			}
		}
	};
</script>