I would do this in a page template.
In your theme, create a file named page-app.php
with the following content:
<?php
/**
* Template Name: App
*/
function wpdev_137109_enqueue_scripts() {
$file="/js/myscript.js";
wp_enqueue_script(
'myscript',
get_stylesheet_directory_uri() . $file,
array( 'jquery' ),
filemtime( get_stylesheet_directory() . $file ),
TRUE
);
$file="/css/mystyle.css";
wp_enqueue_style(
'mystyle',
get_stylesheet_directory_uri() . $file,
array(),
filemtime( get_stylesheet_directory() . $file )
);
} // function wpdev_137109_enqueue_scripts
add_action( 'wp_enqueue_scripts', 'wpdev_137109_enqueue_scripts' );
?>
<?php get_header(); ?>
<div id="sys-mbox">
<textarea id="sys-tbox"></textarea>
</div>
<div class="sys-results">
Total number of words: <span class="words"> </span>
Total number of chars: <span class="character"> </span>
</div>
<?php get_footer(); ?>
Put your stylesheet and script files in the mentioned locations.
Then create a WordPress page and select the page template App from the Page Attributes meta box. Hit save and you’re done.
// EDIT:
As for jQuery, try it like so:
jQuery(function($) {
// code...
});