Fun impossible Firefox JS challenge

Domenic Denicola domenic at
Thu Apr 12 10:48:59 PDT 2012

var tru\u0065; => "Expected identifier" error in IE9.
console.log(fals\u0065) => "Syntax error" in IE9.

Can test IE10 when I get home from work.
From: es-discuss-bounces at [es-discuss-bounces at] on behalf of Brendan Eich [brendan at]
Sent: Thursday, April 12, 2012 13:38
To: Allen Wirfs-Brock
Cc: es-discuss Steen
Subject: Re: Fun impossible Firefox JS challenge

Allen Wirfs-Brock wrote:
> 1) Understand the actual browser interop situation. For example, do
> all major browsers accept:
>       var tru\u0065;

SpiderMonkey shell:

js> var tru\u0065;
typein:1: SyntaxError: missing variable name:
typein:1: var tru\u0065;
typein:1: ....^

It looks like Carakan (Opera), JSC and V8 allow this. I can't test IE.

> 2) Within the constraints of 1) decide what we actually want to
> specify.  Do we want
>       console.log(fals\u0065)
> to print "false" or "undefined"?

Carakan, JSC and V8 alert "undefined".

Anyone have IE results?

Looks like SpiderMonkey implemented ES5 not ES3, probably accidentally
and ahead of time.


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