wp enqueue

function wpdocs_theme_name_scripts() {
    wp_enqueue_style( 'style-name', get_stylesheet_uri() ); /* enqueues style.css */
    /* if you want to enqueue other styles use: */
    /* wp_enqueue_style( 'style-name', get_template_directory_uri() . '/css/your-style-name.css' ); */
    wp_enqueue_script( 'script-name', get_template_directory_uri() . '/js/example.js', array(), '1.0.0', true );
}
add_action( 'wp_enqueue_scripts', 'wpdocs_theme_name_scripts' );

function script_that_requires_jquery() {
    wp_register_script( 'script-with-dependency', 'http://www.example.com/script-with-dependency.js', array( 'jquery' ), '1.0.0', true );
    wp_enqueue_script( 'script-with-dependency' );
}
add_action( 'wp_enqueue_scripts', 'script_that_requires_jquery' );

function my_scripts_method() {
    wp_enqueue_script(
        'custom-script',
        get_stylesheet_directory_uri() . '/js/custom_script.js',
        array( 'jquery' )
    );
}

add_action( 'wp_enqueue_scripts', 'my_scripts_method' );