How to make the chapter title always to the inner or outer side of the page when book is set to openany

Question

I'm using book and have openany set. I'd like to get the chapter titles to by symmetrical--always to the inside or always to the outside of the page. I'm using titlesec. I've looked into an ifthen statement, but failed to get it to work. I know that memoir has an option for this, but if possible I'd like to stay with book so I don't have start over. I'm to the point of thinking this will be more complicated than it's worth and just centering the title.

Answer 1

First solution

Using the page option of \titleformat. Note that you have to redeclare the chapter "class":

\titleclass{\chapter}{top}
\titleformat{name=\chapter,page=odd}[display]
  {\filright\bfseries\Huge}
  {\chaptertitlename\ \thechapter:ODD}
  {2ex}
  {}
\titleformat{name=\chapter,page=even}[display]
  {\filleft\bfseries\Huge}
  {\chaptertitlename\ \thechapter:EVEN}
  {2ex}
  {}

Second solution

Using the \ifodd conditional:

\titleformat{\chapter}[display]
  {\ifodd\thepage\filleft\else\filright\fi
   \bfseries\Huge}
  {\chaptertitlename\ \thechapter}
  {2ex}
  {}
  []