What do you make of this?
var x = {a: 1}; //=> {a: 1}
var y = Object.keys(x); //=> ['a']
x[y] //=> 1
if y = ['a'], x[y] is the same as doing x[['a']], right?
x[['a']]; //=> 1
x[[['a']]]; //=> 1
x[[[[[[[['a']]]]]]]]; //=> 1
Can someone explain what's happening here? Why does this work?
Property names have to be strings. If you try to use an array as a property name, it gets its toString() method called implicitly. That generates a string containing a comma-separated list of its values.
> var array = ['a', 'b', 'c'];
undefined
> array.toString();
'a,b,c'
If you only have one value, then there aren't any commas.
> var array = ['a'];
undefined
> array.toString();
'a'
coma so many comas. Javascript puts me in a coma sometimes. ;)
arr.toString(). Anyway, I've given an answer that shows an actual test case of the behavior you described.@Quentin suggests that property names are automatically converted to strings. Ok, I think he's onto something there, but giving two explicit arr.toString() examples doesn't really demonstrate accessing the property of an object using an array. I offered this as an edit to his post. However, he rolled it back.
Anyway, this demonstrates the implicit behavior much more evidently, imo.
var x = {'a,b,c': 1};
var y = ['a','b','c'];
x[y]; //=> 1
I think it come from 2 facts :
so your
["a"]
when used as a key will be "casted" to string, which give
a
Even
[[[[["a"]]]]].toString() == a // true
so your
x[y]
end un as
x["a"]
a is not a string, to start.
y.toString(), this should get you going ...