Function isMountedVue

src/core/render/index.js:51–56

    Number(window.Vue.version.charAt(0));

  const isMountedVue = elm => {
    const isVue2 = Boolean(elm.__vue__ && elm.__vue__._isVue);
    const isVue3 = Boolean(elm._vnode && elm._vnode.__v_skip);

    return isVue2 || isVue3;
  };

  if (!html) {
    html = '<h1>404 - Not found</h1>';