Number.format() documentation

I've used it in test code and it seemed to work correctly. For example, given the following code

var f = 3.1451234;
Sys.println("%%.2f='" + f.format("%.2f") + "'");


I get this...

%.2f='3.15'


Given a little bit of testing, it seems that the a,A,g,G,e,E specifiers aren't supported. It does appear that the flags, width, and precision specifications are supported for each of the supported specifiers though.

%.2d='03'
%+.2d='+03'
%#.2d='03'
%0.2d='03'
%0.2d='03'
%10.2d=' 03'
% 10.2d=' 03'
%+10.2d=' +03'
% +10.2d=' +03'
%-10.2d='03 '
% -10.2d=' 03 '
%#10.2d=' 03'
%010.2d=' 03'
%010.2d=' 03'
%.2x='03'
%+.2x='03'
%#.2x='0x03'
%0.2x='03'
%0.2x='03'
%10.2x=' 03'
% 10.2x=' 03'
%+10.2x=' 03'
% +10.2x=' 03'
%-10.2x='03 '
% -10.2x='03 '
%#10.2x=' 0x03'
%010.2x=' 03'
%010.2x=' 03'
%.2u='03'
%+.2u='03'
%#.2u='03'
%0.2u='03'
%0.2u='03'
%10.2u=' 03'
% 10.2u=' 03'
%+10.2u=' 03'
% +10.2u=' 03'
%-10.2u='03 '
% -10.2u='03 '
%#10.2u=' 03'
%010.2u=' 03'
%010.2u=' 03'
%.2o='03'
%+.2o='03'
%#.2o='03'
%0.2o='03'
%0.2o='03'
%10.2o=' 03'
% 10.2o=' 03'
%+10.2o=' 03'
% +10.2o=' 03'
%-10.2o='03 '
% -10.2o='03 '
%#10.2o=' 03'
%010.2o=' 03'
%010.2o=' 03'
%.2f='3.14'
%+.2f='+3.14'
%#.2f='3.14'
%0.2f='3.14'
%0.2f='3.14'
%10.2f=' 3.14'
% 10.2f=' 3.14'
%+10.2f=' +3.14'
% +10.2f=' +3.14'
%-10.2f='3.14 '
% -10.2f=' 3.14 '
%#10.2f=' 3.14'
%010.2f='0000003.14'
%010.2f='0000003.14'


That said, this stuff really should have some documentation. I've noticed that Sys.println() (and friends) seem to treat % as the start of a format specification, and that causes bad behavior if you don't escape it as %%.