Login inside the javascript alert

Within alert , but you can get user information through prompt . link

The problem is that this is not a very "friendly" way of getting data. Take a look at whether a modal window within the page itself would meet your requirements:
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This is not exactly a "login to alert", but a login via HTTP Basic Authentication ;

Specifically, this screenshot appears to be a HTTP Basic Authentication fault authentication, and can directly log in to the URL as http://nome:[email protected] .

You can read more about it here.

If you really want to use this type of authentication and break two forms into a single "alert" this is the only solution, as far as you know.

Note that displaying such an alert may change according to the browser, it will not necessarily be shown this way.