JavaScriptで元の配列を変更せずにオブジェクトキーを変更するにはどうすればよいですか？

以下は、JavaScriptで元の配列を変更せずにオブジェクトキーを変更するコードです-

例

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   }
</style>
</head>
<body>
<h1>Change an object Key without changing the original array</h1>
<button class="Btn">CLICK HERE</button>
<h3>
Click the above button to change the name object key to fullName
</h3>
<script>
   let BtnEle = document.querySelector(".Btn");
   let resEle = document.querySelector(".result");
   let sampleEle = document.querySelector(".sample");
   let obj = [
      { name: "Rohan Sharma", age: 12 },
      { name: "Shawn Mendes", age: 18 },
      { name: "Michael Shaw", age: 15 },
      { name: "Mitch Johansson", age: 19 },
   ];
   BtnEle.addEventListener("click", () => {
      obj = obj.map((ele) => {
         ele["fullName"] = ele["name"];
         delete ele["name"];
         return ele;
      });
      console.log(obj);
   });
</script>
</body>
</html>