Internationalization: Normalization and canonical equivalence in string comparison

Norbert Lindenberg ecmascript at
Mon Jun 18 22:36:25 PDT 2012

The ECMAScript Internationalization API Specification currently has normalization as an optional feature in collation. However, it requires that the compare function "return 0 when comparing Strings that are considered canonically equivalent by the Unicode standard". Canonical equivalence, I thought, is usually implemented through normalization. Does it make sense to keep normalization as a separate and optional feature then? Is anybody planning to implement canonical equivalence through other mechanisms, such that the lack of normalization would be visible in the comparison of non-equivalent strings?

BTW, the requirement that canonically equivalent strings compare as equal has been part of the specification of String.prototype.localeCompare since ES3. When testing with a handful of string pairs pulled from chapter 3 of the Unicode Standard and from UTS 10, however, I found that only Opera on the Mac detects their equivalence correctly. Firefox on the Mac and the V8 systems (Chrome, Node) fail to detect any equivalence; Safari, Explorer and the Windows versions of Opera and Firefox detect some and miss others. Obviously people haven't been paying much attention to localeCompare...


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