onChange

.onChange<V>(value: V, action: (values: [V, V]) => void): Component

const body = () => {
    const [name, setName] = useState("")

    return TextField({ text: name, setText: setName })
        .onChange(name, ([oldVal, newVal]) => {
            console.log("Changed from " + oldVal + " to " + newVal)
        })
}

const body = () => {
    const [selected, setSelected] = useState("home")

    return VStack([
        Picker("Tab", [selected, setSelected], [
            Text("Home").tag("home"),
            Text("Profile").tag("profile")
        ])
    ]).onChange(selected, ([oldVal, newVal]) => {
        console.log("Selected: " + newVal)
    })
}

const body = () => {
    const [count, setCount] = useState(0)

    return VStack([
        Text(String(count)),
        Button("Increment", () => setCount(count + 1))
    ]).onChange(count, ([oldVal, newVal]) => {
        if (newVal >= 10) {
            console.log("Reached limit")
        }
    })
}