javascript - 为什么 splice 返回的是字符串而不是数组？

Question

我正在尝试从二维数组 arr 拼接数组 two。

var one = ["a","b"];  
var two = ["c","d"];  
var thr = ["e","f"];  
var arr = [one,two,thr];

这是我的两次失败尝试:

1)

var rem = arr.splice(1,1);  
alert(rem[0]);  
// This alerts the entire array as one long string "c,d".
// The expected behavior is "c" (index 0 of the returned array _rem_).

2)

var rem = arr[1].splice(0);  
alert(arr);  
// The array _rem_ is now correct, but _arr_ is left with an empty index: "a,b,,e,f".

---

我有一个不太理想的解决方法，但我希望通过一个函数来完成。

var test = arr[1].slice(0);  
arr.splice(1,1);

Answer 1

有趣的观察。来自 ECMA 规范(262，第 5 版):

When the splice method is called with two or more arguments start, deleteCount and (optionally) item1, item2, etc., the deleteCount elements of the array starting at array index start are replaced by the arguments item1, item2, etc. An Array object containing the deleted elements (if any) is returned.

Array.splice 因此返回已删除元素的数组。所以，如果你想引用删除的数组，这应该是语法:

var rem = arr.splice(1,1)[0];
alert(rem[0]); //=> 'c'