在数组的第2位置添加一个元素 - splice()

<p id="demo">点击按钮向数组添加元素。</p>

<button onclick="myFunction()">点我</button>

<script>

  function myFunction() {

    var fruits = ["Banana", "Orange", "Apple", "Mango"];

    fruits.splice(2, 0, "Lemon", "Kiwi");

    var x = document.getElementById("demo");

    x.innerHTML = fruits;

  }

</script>