https://www.sitepoint.com/conditionally-applying-css-class-vue-js/
origin - http://www.pipiscrew.com/?p=10208 conditionally-applying-a-css-class-in-vue-js
https://www.sitepoint.com/conditionally-applying-css-class-vue-js/
origin - http://www.pipiscrew.com/?p=10208 conditionally-applying-a-css-class-in-vue-js