[jchw]

That's not really a huge improvement over just making a sparse array though, is it? Looks more confusing to me. Could be wrong but I'm pretty sure e.g. Array(1000000000) does not actually allocate much.

[arve0]

I'm not up to speed in JSX, how is it be better there? Don't one normally map over an array to loop? You cannot use for-loops inside JSX?

Or do you create an array of JSX-elements, like

    let elements=[]
    for (let i=0; i < 10; i++) {
      elements.push(<li key={i}>I'm number {i}</li>)
    }
    return <ol>{elements}</ol>;

Does not seem like an improvement to me.

[jchw]

It's just JS: You can do that, or you can use any helper method, or write your own helper. Can't really do that in Svelte.