確かに！マウス・ポインタにボールを従わせるReact JSXの機能コンポーネントを紹介しよう：
```
import React, { useState } from "react";

function Ball() {
  const [position, setPosition] = useState({ x: 0, y: 0 });

  const handleMouseMove = (event) => {
    setPosition({ x: event.clientX, y: event.clientY });
  };

  return (
    <div
      style={{
        width: "50px",
        height: "50px",
        borderRadius: "50%",
        backgroundColor: "red",
        position: "absolute",
        left: position.x - 25,
        top: position.y - 25,
      }}
      onMouseMove={handleMouseMove}
    ></div>
  );
}

export default Ball;
```
このコードでは、Ballという機能コンポーネントを定義している。useStateフックを使って、ボールの位置状態を管理しています：0 }.handleMouseMove関数を定義し、マウスが動くたびに位置の状態を更新します。最後に、ボールを表す div 要素をレンダリングします。その位置は絶対位置に設定され、left と top の CSS プロパティは位置の状態に基づいて設定されます。また、マウスが動くたびに handleMouseMove 関数を呼び出すように、div 要素に onMouseMove イベントリスナーをアタッチします。
Certainly! Here's a functional component in React JSX that will make a ball follow the mouse pointer:
```
import React, { useState } from "react";

function Ball() {
  const [position, setPosition] = useState({ x: 0, y: 0 });

  const handleMouseMove = (event) => {
    setPosition({ x: event.clientX, y: event.clientY });
  };

  return (
    <div
      style={{
        width: "50px",
        height: "50px",
        borderRadius: "50%",
        backgroundColor: "red",
        position: "absolute",
        left: position.x - 25,
        top: position.y - 25,
      }}
      onMouseMove={handleMouseMove}
    ></div>
  );
}

export default Ball;
```
In this code, we define a functional component called Ball. It uses the useState hook to manage the position state of the ball, which is initialized to { x: 0, y: 0 }. We define a handleMouseMove function that updates the position state whenever the mouse moves. Finally, we render a div element that represents the ball. Its position is set to absolute and its left and top CSS properties are set based on the position state. We also attach the onMouseMove event listener to the div element to call the handleMouseMove function whenever the mouse moves.