teo74wp

never mind, I managed to work for me:

wp_register_script( 'teo_dd', plugins_url( '/msdropdown/jquerydd.min.js'), array( 'jquery-core' ), '20140608', true );
wp_enqueue_script( 'teo_dd' );

without using a function and add_action():

function add_teo_dd(){
	wp_register_script( 'teo_dd', plugins_url( '/msdropdown/jquerydd.min.js'), array( 'jquery-core' ), '20140608', true );
	wp_enqueue_script( 'teo_dd' );
}
add_action('wp_enqueue_scripts', 'add_teo_dd');