ES3 Specification oddness.

Brendan Eich brendan at
Mon May 19 01:53:39 PDT 2008

On May 19, 2008, at 12:56 AM, Steven Mascaro wrote:

> The use of Date makes things look odd, but I assume the spec means
> something like the following:*
> js> function f(){}
> js> f.prototype = {const prop1: 1, prop2: 2}
> js> o = new f
> js> o.prop1 = 42
> 42
> js> o.prop1
> 1
> which is the behaviour I'd expect.
> * I can't find the notation for const's in object literals.

You're using the ES4 syntax; there's no const in ES3.

Yeah, I picked Date but any standard constructor will do (because  
standard constructors have DontDelete + ReadOnly attributes for  
their .prototype properties). So you could s/Date/Object/g, but Date  
suffices and its toString is less anonymous (i.e., not "[object  

Other suitable DontDelete + ReadOnly properties than the standard  
constructors' prototype properties in ES3 include String length,  
Number.MAX_VALUE, etc.

Recollecting more from ES1 days, we did not think about const per se,  
but we did want to prevent ReadOnly properties from being overridden  
in delegates where related properties and methods that depended on  
the ReadOnly value were not overridden, therefore found in a  
prototype. Integrity again.


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