我在理解为什么获得此输出方面有一个小问题.

var arr = ["a", "b", "c", "d", "e", "f"];
arr.splice(2,0,"1");
console.log(arr);  

var arr2 = ["a", "b", "c", "d", "e", "f"];
arr2 = arr2.splice(2,0,"2");
console.log(arr2);

输出是：

[ 'a', 'b', '1', 'c', 'd', 'e', 'f' ]
[]  

为什么输出的第二行不是：

[ 'a', 'b', '2', 'c', 'd', 'e', 'f' ]  

是分配问题还是什么？

解决方法:

阅读约splice方法.它返回

An array containing the removed elements. If only one element is removed, an array of one element is returned.

所以这样做

arr2 = arr2.splice(2,0,"2");

您可以使用splice返回的空数组[]覆盖初始数组arr.