class  {
    onCreate() {
        this.callCount = 0;
        this.state = {
            list: [{
                id: "foo",
                text: "Foo Text"
            }, {
                id: "bar",
                text: "Bar Text"
            }]
        }
    }

    calcKey(id) {
        this.callCount++;
        return `${id}`;
    }

    swap() {
        const [a, b] = this.state.list;
        this.state.list = [b, a];
    }
}

<div.root>
    <for|item| of=state.list>
        <div key=component.calcKey(item.id)>
            ${item.text}
        </div>
        <div>
            Non Keyed ${item.text}
        </div>
    </for>
</div>