Browser support for using a reserved word as a property name in JavaScript

Question

I'm trying to use "for" as an object property name. It seems to work fine in IE7, IE8, Firefox, Chrome and Opera, but apparently not in Safari.

My understanding is that ECMAScript 5 allows it (as discussed in JavaScript keywords in hash keys).

Can I get a definitive list of browsers that support/don't support this somewhere?

EDIT: Actually, CoffeeScript's auto-stringification of reserved word property names is what led me to believe that it works. After re-testing properly it doesn't seem to work anywhere, so the question now is: are there any browsers that allow it as per ECMAScript 5 specification?

Answer 1

There is a table showing browser support for ECMAScript 5 features here: http://kangax.github.com/es5-compat-table/

Reserved words can be used as property names in IE9, Firefox 3.5+ and Chrome 7+, Safari 5.1+.

Answer 2

You can use those words, but only as strings and not shorthand properties.

foo['class']; // cool
foo.class;    // not cool

But here is the actual list you requested. None of these can be used via property dot syntax. https://web.archive.org/web/20140902235313/http://javascript.about.com/library/blreserved.htm

---

Also, only slightly tangential, CoffeeScript notices this and auto stringifies them for you. http://jashkenas.github.com/coffee-script/#literals

Input:

$('.account').attr class: 'active'
log object.class

JS Ouptput:

$('.account').attr({
  "class": 'active'
});
log(object["class"]);

I happen to think that is pretty dang neat.

Answer 3

Perhaps the question is not so much whether reserved words can be used as property names for objects - they can. Seems like the real question here is whether they can be used naked (ie. without being clothed in quotes). Naked use of reserved words is supported from ES5 onwards, but not all interpreters support ES5 features yet. As mentioned, there is a good table here...

http://kangax.github.io/es5-compat-table/#Reserved%20words%20as%20property%20names

If you're just doing some coding in NodeJS, then you don't have to worry about this type of issue. If you care about portability of your code to a wide variety of environments (without using a language like CoffeeScript that compiles to JavaScript), then your code should quote the reserved words...

defining...

var foo = {'for':'this works'};

accessing...

foo ['for'];

Answer 4

after study, I think I can prove that using reserved words as property names (if done with a little common sense) is harmless, whether in the obj['name'] or obj.name syntax.

see this stackoverflow question