svelte/test/js/samples/setup-method/input.html

<script>
	export default {
		methods: {
			foo ( bar ) {
				console.log( bar );
			}
		},
		setup: (Component) => {
			Component.SOME_CONSTANT = 42;
			Component.factory = function (target) {
				return new Component({
					target: target
				});
			}
			Component.prototype.foo( 'baz' );
		}
	};
</script>