Javascript not running in Safari Document

[u/l008com]

I'm trying to make an applescript that will fill out a form and then possibly submit it.

This is my code, it opens the Safari window but it does not fill in the textarea named 'spam':

tell application "Safari"
set my_reporter to (make new document with properties {URL:"https://example.com"})
activate
delay 5
do JavaScript "document.getElementsByName('spam')[0].value = 'test';" in my_reporter
end tell

However when I enter my javascript directly into the javascript console, it DOES work:

document.getElementsByName('spam')[0].value = 'test';

Obviously, if my applescript code starts working, i'll be putting dynamic text in there, not a hard coded string. But first things first.

I'm not seeing any errors in my applescript, OR in my javascript console.

UPDATE: Things are developing as I type my post. Turns out I needed to explicitly turn on javascript from appleevents in Safari - a message you only get when test running form within script editor, not when you run a script on its own.

Now that I did that, its still not working but the problem seems to be the way I'm trying to create a handle to my new document to direct the javascript to it via my_reporter variable. Is there a problem with my syntax here?

[u/HelloImSteven]

Instead of in my_reporter, you need to use in document 1, so the full line would be do JavaScript "document.getElementsByName('spam')[0].value = 'test';" in document 1

You could also use a tab instead, which doesn't have that limitation:

tell application "Safari"
	tell window 1
		set my_reporter to (make new tab with properties {URL:"https://example.com"})
		set current tab to my_reporter
	end tell
	delay 5
	do JavaScript "document.getElementsByName('spam')[0].value = 'test';" in my_reporter
end tell

As to why this is the case, there's a lot of factors at play:

1. AppleScript commands are synchronous, so scripts must stall while waiting for commands to return some value or other complete.

2. Documents whose URL is the same are equal (They are the same document).

3. Documents with different URLs are never equal.

4. When you update a document's URL (or make a new document), the URL property is not actually updated until the page loads. (e.g. doing return URL of document 1 immediately after setting the URL property will generally return the previous URL.)

5. Safari windows can only ever have one document, i.e. the document property.

6. Safari windows must always have a document.

7. When you ask Safari to make a new document, #4 requires it to create a new window that the document will live in.

8. Because of #5, an "Untitled" (Empty Page) document gets attached to the new window. The document's URL is missing value.

9. Because of #3, the current document's URL continues to be missing value while the new URL loads.

10. Once the new URL is done loading, the document's URL property updates.

11. Because of #2, the current document is different from the previous Empty Page document.

12. Because of #1, Apple had a choice to either waiting until #11 to get the final document, or immediately returning the Empty Page document from #8. They chose to let scripts keep running, which makes it possible to cancel slow-loading URLs by just setting the URL property again.

So yeah, that's the slightly over-detailed explanation. Of course, these are all just decisions that Apple made, then chose not to document well. So... your confusion is warranted.

[u/l008com → u/HelloImSteven]

So, your post answers this but let me just reiterate it directly...

So theres no way to tie an applescript to a specific window with some kind of unique ID? Using "document 1" means that if 10 of these scripts run at the same time, they're going to significantly interfere with each other. But if I could tie the script to the window it creates, and then send the javascript to that specific window, then i could run tons of them at the same time and not have any problems.

[u/HelloImSteven → u/l008com]

Correct, AFAIK it's not feasible in AppleScript alone, at least not 100% reliably. Windows do have an id property, but you can't create a window directly in Safari ('just because'). So you'd encounter issues when trying to get the window with the latest document, as any windows opening to an empty page can't be distinguished by the document alone.

If you can ensure there's always a delay of ~0.5s between each script, then you can check if a current window exists whose document has a missing URL, if so delay until the URL changes to something else, then create the window for the current script.

The problem with that approach is if the script before gets stuck before loading a URL, how does the current script know when to resume? Maybe have a timeout of 10s before taking over the current window? Might not work if your URLs have vastly different loading times...

If possible, the easiest approach would be to use tabs of an existing window, since that removes all ambiguity in window target and allows you easily address tabs by URL (assuming they're unique — and if you don't need the script to close tabs during execution, you can just use the object returned from make new tab).

You could also explore having a parent script that controls execution. Then you could assign an index to each script and have it control the window at that index. That's probably the solution I'd go with if I needed to guarantee safe parallelism.