How to check the length of the publication in the wp editor

I am using wp-editor on my homepage (page-id = 22) for the user to write a publication.
This works well

 Publish Content;
} else {
$ af_contet = & # 39; & # 39 ;;
}
$ editor_args = array (
& # 39; wpautop & # 39; => true,
& # 39; media_buttons & # 39; => false,
& # 39; textarea_rows & # 39; => 10,
& # 39; editor_class & # 39; => & # 39; rnm_af_editor & # 39 ;,
& # 39; tabindex & # 39; => 4,
& # 39; tinymce & # 39; => array (
& # 39; theme_advanced_buttons1 & # 39; theme_advanced_buttons1 & # 39; => & # 39; bold, italic, ul, pH, temp & # 39 ;,
)
);

wp_editor
$ af_contet,
& # 39; af_editor_id & # 39 ;, // editor ID (로만)
$ editor_args
);
?>

I want to add a validation code in wp-editor. So I added some js that are queued on this page (jquery is also queued).

$ (& # 39 ;. my-editor & # 39;). in (& # 39; keyup & # 39 ;, & # 39; # af_editor_id & # 39 ;, function () {
if ($ (& # 39; # af_editor_id & # 39;). val (). length> = 10) {
alert (& # 39; This is too short! & # 39;);
}
});

But this does not work. I do not know how to add javascript in wp-editor, particularly the validation after the verification of length.

Can I get help? Thank you.