have you bound your .js file with the proper method ( wp_register_script and wp_enqueue_script )?.
You should do it like this:
// Registering the back-end scripts
add_action( 'wp_enqueue_scripts', 'my_backend_content_scripts' );
// ! Calling the back-end scripts
function my_backend_content_scripts( ) {
if( is_admin() ){
// parameter ( name, script_url, depencys, version, include in header )
wp_register_script( 'my_js', 'www.fullscript_url.com/handsontable.js', array('jquery'), null, true );
wp_enqueue_script( 'my_js');
}
}