Array.includes is not reactive.

const [ activeKeys, setActiveKeys ] = createSignal<number[]> ([])
const isActive = (i: number) => activeKeys ().includes (i)

const [ activeKeys, setActiveKeys ] = createSignal<number[]> ([])
const isActive = (i: number) => activeKeys ().includes (i)

const [ activeKeys, setActiveKeys ] = createSignal<number[]> ([])
const isActive = (i: number) => activeKeys ().includes (i)

const [ activeKeys, setActiveKeys ] = createSignal<number[]> ([])
const isActive = (i: number) => activeKeys ().includes (i)

I have this code. isActive () is not reative.
What's problem?