对这可以通过创建自定义选择性刷新来实现Partial 类型，并重写refresh 方法。

下面是相关的JavaScript，它应该在Customizer预览中排队，使用customize-selective-refresh 作为其脚本依赖项：

wp.customize.selectiveRefresh.partialConstructor.body_class = wp.customize.selectiveRefresh.Partial.extend({

    /**
     * Class name choices.
     *
     * This is populated in PHP via `wp_add_inline_script()`.
     *
     * @type {Array}
     */
    choices: [],

    /**
     * Refresh partial.
     *
     * Override refresh behavior to bypass partial refresh request in favor of direct DOM manipulation.
     *
     * @returns {jQuery.Promise} Resolved promise.
     */
    refresh: function() {
        var partial = this, setting, body, deferred, className;

        setting = wp.customize( partial.params.primarySetting );
        className = setting.get();
        body = $( document.body );
        body.removeClass( partial.choices.join( \' \' ) );
        body.addClass( className );

        // Do good diligence and return an expected value from the function.
        deferred = new $.Deferred();
        deferred.resolveWith( partial, _.map( partial.placements(), function() {
            return \'\';
        } ) );
        return deferred.promise();
    }
});

$wp_customize->selective_refresh->add_partial( \'nav_body_class\', array(
    \'selector\' => \'nav\',
    \'type\' => \'body_class\',
) );