Add SRI attribute to WordPress scripts and stylesheets.

add_sri_attribute.php

<?php

/**
 * Add SRI attributes to external JS resources
 */
function add_sri_attribute($tag, $handle, $src = null)
{
    $known_hashes = array(
        'https://code.jquery.com/jquery-1.12.4.min.js' => 'sha256-ZosEbRLbNQzLpnKIkEdrPv7lOy9C27hHQ+Xp8a4MxAQ=',
    );

    if (!is_ssl() || empty($known_hashes[$src])) {
        return $tag;
    }

    // Append a proper SRI attribute to an element's attribute list.
    $sri_att = ' crossorigin="anonymous" integrity="' . $known_hashes[$src] . '"';
    $insertion_pos = strpos($tag, '>');

    return substr($tag, 0, $insertion_pos) . $sri_att . substr($tag, $insertion_pos);
}

add_filter('style_loader_tag', 'add_sri_attribute', 999999, 3);
add_filter('script_loader_tag', 'add_sri_attribute', 999999, 3);