How to remove all javascript in a theme wordpress?

You either use the admin_*/wp_print_scripts hook or the admin_*/wp_print_styles hook. The styles hook comes before the print scripts hook, so maybe it fits better than just using a priority of 0 for the *_print_scripts hook (there might be function with a name that’s hooked in earlier on priority 0).

function wpse61635_remove_all_scripts()
{
    global $wp_scripts;
    $leave_alone = array(
        // Put the scripts you don't want to remove in here.
    );

    foreach ( $wp_scripts->queue as $handle )
    {
        // Here we skip/leave-alone those, that we added above ↑
        if ( in_array( $handle, $leave_alone ) )
            continue;

        $wp_scripts->remove( $handle );
    }
}
add_action( 'wp_print_styles', 'wpse61635_remove_all_scripts', 0 );