2.1.86 [ECMA-262/6] Section 21.1.3.22 String.prototype.toLowerCase ( )

V0140: Only characters in the Basic Multilingual Plane (values no greater than 0xFFFF) are converted to lowercase

The specification states:

 ... String.prototype.toLowerCase ( )
  
     This function interprets a String value as a sequence of UTF-16 encoded code points, 
     as described in 6.1.4. The following steps are taken:
  
         ...
         ... Let cpList be a List containing in order the code points as defined in 6.1.4 
         of S, starting at the first element of S.
         ... For each code point c in cpList, if the Unicode Character Database provides a 
         language insensitive lower case equivalent of c then replace c in cpList with 
         that equivalent code point(s).

EdgeHTML Mode (All versions)

Only those characters in the Basic Multilingual Plane (values no greater than 0xFFFF) are converted to lower case. Others are left unchanged.

V0139: Results are derived according to the mappings in UnicodeData.txt, but not those in SpecialCasings.txt

The specification states:

 ... String.prototype.toLowerCase ( )
  
     This function interprets a String value as a sequence of UTF-16 encoded code points, 
     as described in 6.1.4. The following steps are taken:
         ...
  
     The result must be derived according to the locale-insensitive case mappings in the 
     Unicode Character Database (this explicitly includes not only the UnicodeData.txt 
     file, but also all locale-insensitive mappings in the SpecialCasings.txt file that 
     accompanies it).

IE11 Mode and EdgeHTML Mode (All versions)

Results are derived according to the mappings in UnicodeData.txt, but not those in SpecialCasings.txt.