I assume these are child theme scripts because of your function name:
twentyfourteen_child_scripts()
When loading scripts from your child themes functions file you should use:
wp_enqueue_script( '$handle', get_bloginfo( 'stylesheet_directory' ) . '/js/filename.js', array( 'jquery' ), '1.0.0' );
Or use
add_action( 'wp_enqueue_scripts', 'child_add_modernizr_scripts' );
function child_add_modernizr_scripts() {
wp_register_script('modernizr', get_stylesheet_directory_uri() . '/js/modernizr.js', false, '1.0', true );
wp_enqueue_script( 'modernizr' );
}
Another potential problem maybe the file names are invalid for some reason.
get_template_directory_uri()
Applies to parent themes.