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Undottability

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  Undottability "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-03-24 11:34 +0100
    Re: Undottability Martin Honnen <mahotrash@yahoo.de> - 2013-03-24 12:02 +0100
      Re: Undottability "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-03-24 19:50 +0100
        Re: Undottability Martin Honnen <mahotrash@yahoo.de> - 2013-03-26 11:59 +0100

#18982 — Undottability

var a = {};

a[''] = 9;
alert(a['']); // 9

[chrome tested]

This object property seems undottable,
as you cannot write it like:

a.b = 1;
alert(a.b); // 1

Strangerder js?

-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#18983

Evertjan. wrote:
> var a = {};
>
> a[''] = 9;
> alert(a['']); // 9
>
> [chrome tested]
>
> This object property seems undottable,
> as you cannot write it like:
>
> a.b = 1;
> alert(a.b); // 1
>
> Strangerder js?

Well generally property names are strings and the "dot" notation only 
works for those strings that are identifiers. So the general property 
access notation is the "bracket" notation, not the "dot" notation.

But that is nothing new, is it? When PHP required a group of input 
controls to be named 'foo[]' e.g.
   <input type="radio" name="foo[]" ...>
then you always needed the bracket notation in Javascript to access 
them, as in
   document.forms.formName.elements['foo[]'][0]

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#18987

Martin Honnen wrote on 24 mrt 2013 in comp.lang.javascript:

> Evertjan. wrote:
>> var a = {};
>>
>> a[''] = 9;
>> alert(a['']); // 9
>>
>> [chrome tested]
>>
>> This object property seems undottable,
>> as you cannot write it like:
>>
>> a.b = 1;
>> alert(a.b); // 1
>>
>> Strangerder js?
> 
> Well generally property names are strings and the "dot" notation only 
> works for those strings that are identifiers. So the general property 
> access notation is the "bracket" notation, not the "dot" notation.

Okay.

So they are always strings, even the empty string,
and a number is converted to a string first?

var a = {};

a['8'] = 2;
a[08] = 9;

alert(a['8']); // 9
alert(a[8]); // 9

a['08'] = 2;
alert(a[8]); // 9

a['8'] = 1;
alert(a[8]); // 1

alert(a.length); // undefined [not an array]


> But that is nothing new, is it? When PHP required a group of input 
> controls to be named 'foo[]' e.g.
>    <input type="radio" name="foo[]" ...>

Well, I don't speak php, 
why would it require that in this example?

> then you always needed the bracket notation in Javascript to access 
> them, as in
>    document.forms.formName.elements['foo[]'][0]

-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

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#18991

Evertjan. wrote:

> So they are always strings, even the empty string,
> and a number is converted to a string first?

Yes, see http://www.ecma-international.org/ecma-262/5.1/#sec-11.2.1, the 
expression in square brackets is evaluated first and then the result of 
the evaluation is converted to a string.

>> But that is nothing new, is it? When PHP required a group of input
>> controls to be named 'foo[]' e.g.
>>     <input type="radio" name="foo[]" ...>
>
> Well, I don't speak php,
> why would it require that in this example?


I think for PHP server-side code to handle a group of input element 
values (like a group of checkboxes or radio buttons) as an array the 
naming convention "groupName[]" with the suffix "[]" is required.

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