JavaScriptで2つの配列を結合する方法は？

以下は、JavaScriptで2つの配列を結合するコードです-

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;
   }
   .result,.sample {
      font-size: 18px;
      font-weight: 500;
      color: rebeccapurple;
   }
   .result {
      color: red;
   }
</style>
</head>
<body>
<h1>Join two arrays in JavaScript</h1>
<div class="sample"></div>
<div class="result"></div>
<button class="Btn">CLICK HERE</button>
<h3>Click the above button to join the above two arrays together.</h3>
<script>
   let BtnEle = document.querySelector(".Btn");
   let resEle = document.querySelector(".result");
   let sampleEle = document.querySelector(".sample");
   let arr = [1, 2, 3, 4];
   let arr1 = ["A", "B", "C", "D"];
   sampleEle.innerHTML = "arr = " + arr + " " + "arr1 = " + arr1;
   let mergedArr = arr.concat(arr1);
   BtnEle.addEventListener("click", () => {
      resEle.innerHTML = "Merged array = " + mergedArr;
   });
</script>
</body>
</html>