How to use the heyui/utils/utils.addClass function in heyui

function Message(content, timeout, type, onClose) {
  if (!messageDom) {
    messageDom = document.createElement('div');
    utils.addClass(messageDom, `${prefixCls}-container`);
    document.body.appendChild(messageDom);
  }
  let param = {
    type: prefixCls,
    content: `<div><i class="${iconPrefixCls}-${iconNames[type]} ${iconColor[type]}-color"></i>${content}</div>`,
    event: {
      close: onClose
    },
    timeout,
    parent: messageDom
  };
  param = utils.extend({}, Default, param, true);
  if (param.timeout &lt; 1) param.hasCloseIcon = true;
  return Notify(param);
}

<div class="${loadingCls}-circular">
        <svg viewBox="25 25 50 50">
          <circle class="circle" fill="none" r="20" cy="50" cx="50"></circle>
        </svg>
        <p class="${loadingCls}-text">${content}</p></div>
      
    `;
    let genDom = window.document.createElement('div');
    genDom.innerHTML = template;
    LoadingDom = genDom.childNodes[0];
    document.body.appendChild(LoadingDom);
  } else {
    LoadingDom.querySelector(`.${loadingCls}-text`).innerText = content;
  }
  utils.addClass(LoadingDom, `${loadingCls}-loading`);
  utils.addClass(LoadingDom, `${loadingCls}-visible`);
}

let template = `<div class="${loadingCls} ${loadingCls}-full-screen">
      <div class="${loadingCls}-circular">
        <svg viewBox="25 25 50 50">
          <circle class="circle" fill="none" r="20" cy="50" cx="50"></circle>
        </svg>
        <p class="${loadingCls}-text">${content}</p></div>
      </div>
    `;
    let genDom = window.document.createElement('div');
    genDom.innerHTML = template;
    LoadingDom = genDom.childNodes[0];
    document.body.appendChild(LoadingDom);
  } else {
    LoadingDom.querySelector(`.${loadingCls}-text`).innerText = content;
  }
  utils.addClass(LoadingDom, `${loadingCls}-loading`);
  utils.addClass(LoadingDom, `${loadingCls}-visible`);
}

this.$nextTick(() => {
          utils.addClass(this.$el, 'h-loading-loading');
          utils.addClass(this.$el, 'h-loading-visible');
          let parent = this.$el.parentNode;
          if (parent) {
            utils.addClass(parent, 'h-loading-parent');
          }
        });
      } else {

this.$nextTick(() => {
          utils.addClass(this.$el, 'h-loading-loading');
          utils.addClass(this.$el, 'h-loading-visible');
          let parent = this.$el.parentNode;
          if (parent) {
            utils.addClass(parent, 'h-loading-parent');
          }
        });
      } else {

this.$nextTick(() => {
          utils.addClass(this.$el, 'h-loading-loading');
          utils.addClass(this.$el, 'h-loading-visible');
          let parent = this.$el.parentNode;
          if (parent) {
            utils.addClass(parent, 'h-loading-parent');
          }
        });
      } else {