Enqueue IE (Internet Explorer) only scripts and stylesheet in WordPress

wp-conditional-enqueue-new-way.php

<?php
function op_enqueue_scripts() {
    wp_enqueue_style(
        'op-ie8',
        get_template_directory_uri() . '/assets/css/ie8.css',
        array(),
        '0.0.7'
    );
    wp_style_add_data( 'op-ie8', 'conditional', 'IE 8' );
    
    wp_enqueue_script(
        'respond',
        get_template_directory_uri() . '/assets/vendor/respond.min.js',
        array(),
        '0.0.7',
        false
    );
    wp_script_add_data( 'respond', 'conditional', 'IE 8' );
}
add_action( 'wp_enqueue_scripts', 'op_enqueue_scripts' );

wp-conditional-enqueue-old-way.php

<?php
function op_enqueue_conditional_script() {
    ?>
    <!--[if IE 8]>
    <script type="text/javascript" src="<?php echo get_template_directory_uri(); ?>/assets/vendor/respond.min.js"></script>
    <![endif]-->
    <?php
}
add_action( 'wp_head', 'op_enqueue_conditional_script' );