marijnh/Eloquent-JavaScript — pull request #152 by xfq (2014-12-18 11:57:51+00:00)
Title: Update 04_data.txt

Property names must be strings. Although the code here works (2 is type-casted into "2"), IMHO using strings consistently is better.

Spec: http://www.ecma-international.org/ecma-262/5.1/#sec-11.2.1