Applescript: Safari "Do Javascript" No Longer Returns Booleans?

Question

This used to return either true or false:

tell application "Safari" to do JavaScript "document.querySelector(\"video\") == null" in document 1

However, now, on macOS 12.0.1 on an M1 MBP, it doesn't seem to return anything (missing value) and the following convoluted wrapper seems necessary to get the former result:

tell application "Safari"
    set result to do JavaScript "if (document.querySelector(\"video\") == null) {
   1
} else {
   0
}" in document 1
    return result is 1
end tell

Another weird thing is that it's only booleans that don't get returned. The following returns 3.0:

tell application "Safari" to do JavaScript "3" in document 1

Any idea what changed? Is there a better way to get the boolean result back?

Here is what my Safari Develop tab looks like in case any of those settings are relevant:

Answer 1

I still don't know why the issue is happening, but here's a temporary workaround in case it helps:

tell application "Safari"
    
    set result to do JavaScript "try {
    var jsResult = document.querySelector(\"video\").paused;

    switch (jsResult) {
    case true:
        jsResult = 'js2as-true';
        break;
    case false:
        jsResult = 'js2as-false';
    }
jsResult
}
catch(err) {
'js2as-error' + err.message
}" in document 1
    
    if (result = "js2as-true") then
        return true
    else if (result = "js2as-false") then
        return false
    else if (result starts with "js2as-error") then
        set errMsg to text 12 thru -1 of result
        error errMsg
    else
        return result
    end if
end tell

One limitation is that it's hard to make generic because you need to explicitly store the return value from the appropriate statement. Another approach might be to insert the script into an anonymous function, but then you'd have to explicitly return aValue