discourse/app/assets/javascripts/admin/addon/components/highlighted-code.js

import { observes, on } from "@ember-decorators/object";
import Component from "@ember/component";
import highlightSyntax from "discourse/lib/highlight-syntax";

export default class HighlightedCode extends Component {
  @on("didInsertElement")
  @observes("code")
  _refresh() {
    highlightSyntax(this.element, this.siteSettings, this.session);
  }
}