How to "Wait until web page loaded" in Firefox (applescript)? - firefox

Question

This code from here works perfect, but doesn't work in Firefox. Why and how to fix it in applescript?
tell application "Google Chrome"
repeat until (loading of tab 1 of window 1 is false)
1 + 1 --just an arbitary line
end repeat
loading of tab 1 of window 1 --this just returns final status
end tell

Answer 1

As Firefox does not contain a specific AppleScript dictionary, e.g. Firefox.sdef file, it is not considered to be AppleScript scriptable in the same way as e.g. Google Chrome, and while it will respond to some of the basic commands, such as activate, quit, etc., it will require UI Scripting to do what you are asking.
The following example AppleScript code requires Firefox version 87 or newer, and setting its accessibility.force_disabled preference to: -1
First, in Firefox, in the Address/Search combo box, type about:config and press enter.
If applicable, click the Accept the Risk and Continue button.
In the Search preference name text box, type accessibility.force_disabled and press enter.
Click the Edit button and change its value to: -1
Click the the Save button.
Here is an example of how I would instruct Firefox to open a new window to a given URL and wait for the page to finish loading.
Example AppleScript code:
set theURL to "https://news.google.com/"
tell application "Firefox" to activate
delay 0.5 -- # Value may need to be adjusted if Firefox is closed.
my clickApplicationMenuCommand("Firefox", "File", "New Window")
delay 0.5
my setURLofFirefoxFrontWindowTo(theURL)
my waitForFirefoxPageToFinishLoading()
say "foobar"
-- # Handler(s) #
to clickApplicationMenuCommand(appName, appMenuName, appMenuCommand)
tell application appName to activate
delay 0.25
tell application "System Events" to ¬
click ¬
menu item appMenuCommand of ¬
menu appMenuName of ¬
menu bar item appMenuName of ¬
menu bar 1 of ¬
application process appName
end clickApplicationMenuCommand
to setURLofFirefoxFrontWindowTo(theURL)
tell application "System Events"
tell application process "Firefox"
set the value of UI element 1 of ¬
combo box 1 of toolbar "Navigation" of ¬
first group of front window to theURL
key code 36 -- # enter key
end tell
end tell
end setURLofFirefoxFrontWindowTo
to waitForFirefoxPageToFinishLoading()
-- # Requires Firefox version 87 or newer.
-- # Requires accessibility.force_disabled set to: -1
tell application "System Events"
tell application process "Firefox"
repeat until exists UI element "Reload" of ¬
toolbar "Navigation" of group 1 of window 1
delay 0.1
end repeat
repeat while (name of UI elements of ¬
toolbar "Navigation" of group 1 of ¬
window 1 whose description is "Reload") ¬
is not {"Reload"}
delay 0.1
end repeat
end tell
end tell
end waitForFirefoxPageToFinishLoading
Notes:
The example AppleScript code, shown above, was tested in Script Editor under macOS Catalina with Language & Region settings in System Preferences set to English (US) — Primary and worked for me without issue1.
1 Assumes necessary and appropriate settings in System Preferences > Security & Privacy > Privacy have been set/addressed as needed.
Tested using Firefox version 91.0 (64-bit).
Note that UI Scripting is very kludgy and is prone to failure, especially as the version of the OS and or application change, or the value of the delay commands are not sufficient. That said however, with Firefox, this as described herein is what it takes.
Note: The example AppleScript code is just that and sans any included error handling does not contain any additional error handling as may be appropriate. The onus is upon the user to add any error handling as may be appropriate, needed or wanted. Have a look at the try statement and error statement in the AppleScript Language Guide. See also, Working with Errors. Additionally, the use of the delay command may be necessary between events where appropriate, e.g. delay 0.5, with the value of the delay set appropriately.