Azure AD B2C - Set custom claim value from Javascript

I want to add a JS component that I've built to my custom policy's HTML template.

This component will output a string that I want to send as a claim when the form is submitted.

For example: a user clicks the component and it returns the string "123". The value "123" will be sent as a custom claim to the rest of the custom policy execution.

1. Can I use JS in the custom HTML to import the module and inject it to the HTML?
2. Is there a way to set a custom claim's value using JS from that component?