Following is my code, attr y is translate y not "y in svg", I expect find attr svgY to set "y in svg", how to do?

    var it: SVGTextElement
    ReactDOM.render(<svg>
        <text ref={e => it = e} y={10}>pr</text>
    </svg>, document.querySelector("#root"))
    var by = it.getBBox().y
    console.log(`by:${by}`) // by:-4.34375