Using the OnDOMReady Event

We recommend performing all JavaScript initialization within the OnDOMReady event-- this is called when the page has finished parsing the document and has loaded the DOM into memory.

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Scripts may execute before this event!

Some scripts on the page may execute before OnDOMReady is called. If you need to initialize JavaScript on the page before any scripts are executed, you should use LoadListener::OnWindowObjectReady instead.

Why don't we just always use OnWindowObjectReady?

The caveat of using OnWindowObjectReady is that it is only called on pages that have scripts on them, also you can't do any DOM manipulation in that event since the DOM is incomplete. In contrast, OnDOMReady is always called, just after the DOM has loaded.

Attaching with the LoadListener interface

This event is part of the LoadListener interface, we will inherit from it and bind it to our View.

#include <Ultralight/Ultralight.h>

using namespace ultralight;

class MyListener : public LoadListener {
public:
  MyListener(View* view) {
    view->set_load_listener(this);
  }
  
  virtual ~MyListener() {}
  
  ///
  /// Use LoadListener::OnDOMReady to wait for the DOM to load.
  ///
  virtual void OnDOMReady(View* caller,
                          uint64_t frame_id,
                          bool is_main_frame,
                          const String& url) override {
    ///
    /// Initialize the page here with JavaScript.
    ///
  }
};