删除位于 index 2 的元素，并添加一个新元素来替代被删除的元素

<script type=”text/javascript”>
var arr = new Array(6)
arr[0] = “George”
arr[1] = “John”
arr[2] = “Thomas”
arr[3] = “James”
arr[4] = “Adrew”
arr[5] = “Martin”
document.write(arr + “<br />”)
arr.splice(2,1,”William”)
document.write(arr)
</script>

输出：
George,John,Thomas,James,Adrew,Martin
George,John,William,James,Adrew,Martin