See the example here >>> https://www.readcereal.com/wp-content/themes/cereal/js/main.singlePost.js?ver=1.0 and live demo here >>> https://www.readcereal.com/fort-of-the-sun/

wrap all same classes element.js

// wrap images with class of portrait into a group for styling
$(function(){
    var cWrap=$('<div class="portrait-set clear"></div>');
    $('.articleImages figure.portrait').each(function(){
        var o = $(this).next('figure.portrait').length;
        $(this).replaceWith(cWrap).appendTo(cWrap);
        if (!o) cWrap=$('<div class="portrait-set clear"></div>');
    });
});