http://mathias.html5.org/specs/javascript/#escaped-reserved-words says:
> JavaScript implementations must support ECMAScript identifiers that unescape > to a reserved word, as long as at least one character is escaped using a > Unicode escape sequence. > > For example, var var; throws a syntax error, but e.g. var v\u0061r; works > fine. > > Subsequent use of such identifiers must also have at least one character > escaped (otherwise the reserved word will be used instead), but it doesn’t > have to be the same character(s) that were originally used to create the > identifier. > > For example, var v\u0061r = 42; alert(va\u0072); alerts 42. One year ago, all browsers except IE fulfilled this compatibility requirement. Half a year ago Firefox dropped this non-standard addition (https://bugzilla.mozilla.org/show_bug.cgi?id=694360) and hasn’t seen any compatibility issues since. Has the time come to drop this compatibility requirement?
