SSO Form Client-Initiated javascript issue

Trying to create an SSO form based configuration to submit data (username and password) using javascript function which is triggered by an onlick event on a button.

There is no form on the page, javascript gets the below parameters when the button is clicked.

Sign In

I have configured the form parameters under parameter settings and form detection, this seems to be working as i get this in the logs:

SSOv2 Request match, config /Common/test-sso-form form testform
SSOv2 Request "GET /clients.html", config /Common/test-sso-form

As there is no form or submit button i am assuming the data is not being sent so i looked at injecting javascript to call the login function but sso does not log me in.

Could you advise what the correct method would be to call login_function?

I have tried this the below javascript injection (custom) i found from another dev article but does not sign me in.

I have tried various combinations with the above to trigger the function like not setting the username and password values in javascript because it is done with the form parameters already?

Any help to put me on the right track would be great.