<p>bar in Foo: {{bar}}</p>
<p>baz in Foo: {{baz}}</p>

<script>
	export default {
		data() {
			return {
				bar: 1,
				baz: 2
			};
		},

		methods: {
			double() {
				const { bar, baz } = this.get();
				this.set({ bar: bar * 2, baz: baz * 2 });
			}
		}
	};
</script>