Why does splice return a string instead of an array?

Question

I'm trying to splice array two from the two-dimensional array arr.

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

Here are my two unsuccessful attempts:

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".

---

I have a less than ideal workaround, but I'm hoping to accomplish this with one function.

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

Answer 1

Interesting observation. From the ECMA-specs (262, ed. 5):

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 thus returns an array of the removed elements. So, if you want to reference the removed array, this should be the syntax:

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

Answer 2

You seem confused, possibly by what happens when you pass an array to alert(). From what I can tell of what you want, your first example is correct. Before doing any splicing, what you have in your arr variable is

[
   ["a", "b"],
   ["c", "d"],
   ["e", "f"]
]

After calling var rem = arr.splice(1, 1), which removes one element from arr at index 1 and stores it in an array in variable rem, what you have is

arr:

[
   ["a", "b"],
   ["e", "f"]
]

rem:

[
   ["c", "d"]
]

So rem[0] is the array ["c", "d"], which is what I thought you wanted.

Answer 3

I think its working as expected splice method always returns an array.

when you say arr[1].splice(0); its calling spilce on one and gives ['a']

And when you do arr.splice(1,1); it will return [one]