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From: Asen Bozhilov on 12 Apr 2010 17:09
Garrett Smith wrote:

> That's useful, but not really directly related to "Square Bracket
> Notation". It seems out of place for that article.

Yes, that is not related with property access notations, but can it in
addition. And general idea is to show distinctions between property
names in square bracket notation, dot notation and property names in
object literals. In object literal cannot be used result of expression
for property name. That is the main difference with square bracket
notation, where result of any valid expression by ECMA-262 can be used
as property name. The difference with dot notation where property name
is an Identifier, in object literal as property name can be used
NumericLiteral and StringLiteral. So any valid Indentifier,
NumericLiteral and StringLiteral can be used as property name. For
example, the follow property names are syntactical valid by rules in
ECMA-262-3 11.1.5 Object Initialiser:

var obj = {
propertyName : true,
2 : true,
'function' : true
};

And the follow are not, because are not valid Identifier,
StringLiteral or NumericLiteral:

var obj1 = {
function : false,
2 + 2 : false,
'str\' : false
};

Another purposes to I suggested update of article is because ES5 does
changes in dot notation and object literal for PropertyName. There is
used IdentifierName instead of Identifier, which mean ReservedWords in
ECMA-262-5 can be used as property name in dot notation.

| ECMA-262-5 11.2.1 Property Accessors

| Properties are accessed by name, using either the dot notation:
| MemberExpression . IdentifierName
| CallExpression . IdentifierName

And in ES5 implementation the follow property access expressions are
syntactical valid:

myObj.function;
myObj.super;

And follows are invalid:

myObj.0;
myObj.\u0030;

You can see some new things in ES5 by kangax slides.
<URL: http://www.slideshare.net/kangax/say-hello-to-ecmascript-5 />
For my words see slide 46.
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