docs: function btnOnClick(e, opts, callback, target, k) {
          var that = void 0;
          if (e.srcElement) e.target = e.srcElement;
  
          target = U.findParentNode(e.target, function (target) {
            if (target.getAttribute("data-modal-header-btn")) {
              return true;
            }
          });
  
          if (target) {
            k = target.getAttribute("data-modal-header-btn");
  
            that = {
              self: this,
              key: k,
              value: opts.header.btns[k],
              dialogId: opts.id,
              btnTarget: target
            };
  
            if (opts.header.btns[k].onClick) {
              opts.header.btns[k].onClick.call(that, k);
            }
          }
  
          that = null;
          opts = null;
          callback = null;
          target = null;
          k = null;
        }