TypeError: document.write is not a function

[ssb22]

Hi, thanks for implementing LightPanda which I'm hoping to be able to use with my web-accessibility proxy so that blind users will have the option of using text-mode browsers that don't support Javascript themselves.

However, I noticed that any attempt to use document.write (during page load) gives TypeError: document.write is not a function whereas it's one of the earliest DOM-modifying functions around (it predates innerHTML). Is this just "not implemented yet" or was there a deliberate decision not to support it for some reason?

Thanks.

[krichprollsch]

@ssb22, thanks for the issue.

Indeed, we didn't implement document.write mostly because it is a deprecated function according with https://developer.mozilla.org/en-US/docs/Web/API/Document/write and removed from DOM standard.

Is the document.write used by your script? or do you have an example of websites using it?

[ssb22]

Thanks, I'm afraid many websites still use document.write because, as shown on the compatibility table at the bottom of that link, all the current mainstream browsers still support it, therefore Web developers are not rushing to remove it from existing code even though it's deprecated.

Most actual uses of document.write I've seen are to do with analytics tracking and email address obfuscation, but we can't rule out the possibility that some sites may break without it. Moreover, a new user of LightPanda may think (as I did) that document.write would make a good "hello world" test to see if Javascript is working, since it was the oldest and most-supported document-manipulation function around. (I remember when I coded Web Adapter for WiderWeb & OpenWave 20 years ago we had document.write working a long time before we had innerHTML working.)

As a short-term solution (because we don't know how long it will be around after deprecation) I suppose you could provide an emulation of document.write that's good enough for most purposes simply by injecting an extra piece of script like:

document.write = (html) => {
    const d = document.createElement("div");
    d.innerHTML = html;
    for(var c; (c=d.firstChild) != null; document.body.appendChild(c));
}

This won't behave exactly the same, especially when document.readyState is not loading or the document.write is being given unfinished HTML fragments, but at least it should serve to make most real-world uses of document.write work while we're waiting for the world to catch up with the deprecation.

[krichprollsch]

@ssb22 thanks for your feedback. I merged #1274 which implement document.open, document.close and document.write.
I don't think it's perfect, but it should work correctly for basic usages.
It will be available in the nightly build starting tomorrow.

Let-me know if it fixes the issue.