ToString for Numbers: reducing variation.

David Jones drj at
Fri Jul 11 07:41:01 PDT 2008

After I wrote a blog article on this subject someone suggested I  
raise the issue here.

Currently, ECMA 262 3rd edition section 9.8.1, the ToString operator  
permits implementations to vary in how they convert certain numbers  
to strings.  For example the number 5e-324 could legally be converted  
as "3e-324", "4e-324", and so on up to "7e-324".

This would permit an implementation to evaluate the following  
expression as "undefined":


I do not think any reasonable implementation would have a good reason  
for doing this.

It also permits the value of 'a' to vary between implementations in  
the following loop body:

for(a in {5e-324:true}) {...}

In order to ensure implementations all behave the same way I suggest  
the note at end of section 9.8.1 be moved to normative status.  As  
far as I can tell, the text is essentially the same between ECMA 262  
3rd edition and the Oslo draft published on 2008-07-04.


PS blog article at: 

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