observe(eventName, handler) -> document

Listens for the given event over the entire document. Can also be used for listening to "dom:loaded" event.

document.observe is the document-wide version of Element#observe. Using document.observe is equivalent to Event.observe(document, eventName, handler).

The "dom:loaded" event

One really useful event generated by Prototype that you might want to observe on the document is "dom:loaded". On supporting browsers it fires on DOMContentLoaded and on unsupporting browsers it simulates it using smart workarounds. If you used window.onload before you might want to switch to dom:loaded because it will fire immediately after the HTML document is fully loaded, but before images on the page are fully loaded. The load event on window only fires after all page images are loaded, making it unsuitable for some initialization purposes like hiding page elements (so they can be shown later).

Example

document.observe("dom:loaded", function() {
  // initially hide all containers for tab content
  $$('div.tabcontent').invoke('hide');
});