Javascript when dom is ready

At the end of the body, DOM is appropriately rendered and ready. So, there are no issues with function calls related to any element. It works much faster than the body onload handler because it does not wait for the images to be loaded completely.

DelftStack is a collective effort contributed by software geeks like you. If you like the article and would like to contribute to DelftStack by writing paid articles, you can check the write for us page. It sends the data in background. The transition to another page is not delayed: the browser leaves the page, but still performs sendBeacon.

You can find more information in the chapter Fetch API. But we can use another event — onbeforeunload. If a visitor initiated navigation away from the page or tries to close the window, the beforeunload handler asks for additional confirmation.

For historical reasons, returning a non-empty string also counts as canceling the event. The behavior was changed, because some webmasters abused this event handler by showing misleading and annoying messages. Instead, in such handlers one should set event. There are cases when we are not sure whether the document is ready or not.

So we can check document. The readystatechange event is an alternative mechanics of tracking the document loading state, it appeared long ago. Nowadays, it is rarely used. As this code is listening for when elements are rendered, the MutationObserver must be setup before the element you are looking for in the HTML. For more things you can do with MutationObservers , take a look at our article on the topic.

If you are waiting on a specific resource, you can bind to the load event of just that element. Note that if the image fails to load for some reason, the load event will never fire. You can, however, bind to the error event in the same manner, allowing you to handle that case as well.