marko/packages/runtime-class/test/components-browser/fixtures/destroy-cleanup/component.js

module.exports = {
  onMount() {
    const root = this.getEl("root");
    this.before = document.createElement("span");
    this.before.id = "before";
    root.parentNode.insertBefore(this.before, root);
  },
  onDestroy() {
    this.before.remove();
  },
};