Someone remended here that window.onpaint be used to run some javascript before page load. I've never actually seen this before, could someone explain its usage/usefulness?

Someone remended here that window.onpaint be used to run some javascript before page load. I've never actually seen this before, could someone explain its usage/usefulness?

• javascript

2 Answers 2

From the MDN :

onpaint doesn't work currently, and it is questionable whether this event is going to work at all, see bug 239074.

So the usefulness is zero.

It might depend on your exact use case but if you want to run a script "before page load", the simplest solution is probably to put it in the head.

[UPDATE 2025]

Looking at MDN, there is no reference to any paint event existing on the window object and there is no reference to any window.onpaint method, even in the list of deprecated methods. After searching on the internet, there is no reference of such method, except the two Stackoverflow questions (this one and the one mentioned in the question) and the Mozilla discussion mentioned by Kyle Marimon.

The HTML5/DOM window specification (https://www.w3/TR/2008/WD-html5-20080610/web-browsers.html#window) has no reference to such event or function.

Last but not least, window.onpaint is never called automatically by the browser. A simple test can be done:

    <script>
        window.onpaint = () => {
            console.log("hello stackoverflow from window.onpaint()")
        }
    </script>

The snippet above won't log anything into the console.

In other words, feel free to define window.onpaint but don't expect this function to be called when initializing the DOM.