B2G/gecko/toolkit/components/osfile/ospath_win_back.jsm
/**
      * Return the drive letter of a path, or |null| if the
      * path does not contain a drive letter.
      */
Return the drive letter of a path, or |null| if the
path does not contain a drive letter.
Return the drive letter of a path or |null| if the path does not contain a drive letter .
function winGetDrive(path) {
       ensureNotUNC(path);
       let index = path.indexOf(":");
       if (index <= 0) return null;
       return path.slice(0, index + 1);
     }
function winGetDrive ( path ) { ensureNotUNC ( path ) ; let index = path . indexOf ( ":" ) ; if ( index <= 0 ) return null ; return path . slice ( 0 , index + 1 ) ; }
Return the drive letter of a path, or |null| if the
 path does not contain a drive letter.
Return the drive letter of a path or |null| if the path does not contain a drive letter .