Javascript の連想配列で key に数値を入れると文字列になるメモ

$ node

> var a = {1: 'a', 2: 'b', 3: 'c'}
undefined
> a
{ '1': 'a', '2': 'b', '3': 'c' }
> Object.keys(a)[0]
'1'
> typeof Object.keys(a)[0]
'string'

ちなみに Python だと数値のまま

$ ipython

In [1]: a = {1: 'a', 2: 'b', 3: 'c'}

In [2]: a
Out[2]: {1: 'a', 2: 'b', 3: 'c'}

In [3]: a.keys()[0]
Out[3]: 1

In [4]: type(a.keys()[0])
Out[4]: int