<ifmodule mod_rewrite.c>
    rewriteengine on
    rewritebase /subdirectory
    rewriterule ^index\.html$ - [l]
    rewritecond %{request_filename} !-f
    rewritecond %{request_filename} !-d
    rewritecond %{request_filename} !-l
    rewriterule . /index.html [l]
</ifmodule>