Here's your Hello World in real Qt code for reference:

    import QtQuick 2.7
    import QtQuick.Controls 2.2
    ApplicationWindow
    {
        title: "Example"
        Button {
            height: 300
            width: 300 
            x: 50
            y: 50 // not represented in the react code for some reason

            onClicked: console.log("Hello")
        }
    }