Use the Run JavaScript on Web Page action in Shortcuts on iPhone or iPad
Use the Run JavaScript on Web Page action to retrieve specific data from a website, or to modify the contents of a web page.
The Run JavaScript on Web Page action contains a text field where you write your own script. You run the shortcut from the Safari app. Before you can run JavaScript from a shortcut, you must turn on Allow Running Scripts. See Advanced Privacy and security settings in Shortcuts on iPhone or iPad.
Note: You can also use the Run JavaScript on Web Page action in SFSafariViewController. For more information, see https://developer.apple.com/documentation/safariservices/sfsafariviewcontroller.
Create a JavaScript shortcut
In the Shortcuts app
on your iPhone or iPad, tap 
in the upper-right corner of the screen.In the shortcut editor, tap
the search field at the bottom of the screen, begin typing “Run JavaScript…” in the search field, then tap the Run JavaScript on Webpage action to add it to the shortcut editor.Write your script in the text field in the Run JavaScript on Web Page action.
Important: In your script, make sure you call the completion handler. For more information, see Run JavaScript on Web Page action output.
Add any other actions you want to include in the shortcut.
Tip: To use multiple Run JavaScript on Web Page actions in the same shortcut, make sure each instance of the action has the Safari web page as its input.
Tap
to open Details, then turn on Show in Share Sheet.A new row labelled “Receive” appears. To ensure that the shortcut appears only in Safari, deselect all input types except “Safari webpages”.
For more information, see Understanding input types in Shortcuts on iPhone or iPad.
Tap Done to return to the shortcut editor, then tap Done again to save the shortcut to your shortcuts collection.
For more information about working with JavaScript in Shortcuts, see Intro to the Run JavaScript on Web Page action in Shortcuts on iPhone or iPad.
Run the JavaScript shortcut on a web page
In Safari on your iPhone or iPad, tap
.Tap a shortcut containing the Run JavaScript on Web Page action.
Note: You can also run the shortcut in SFSafariViewController.