How to enable Flash Player in the browser via Javascript?

There is no official way to enable Flash using only Javascript, if they figure out how to do this it will possibly be treated as a security issue.

About play.spotify.com/browse , it clearly asks the user to enable manually , this does not requires JS, but rather interpreting the browser by clicking https://get.adobe.com/flashplayer/ ,

Use this:

<a href="https://get.adobe.com/flashplayer/" target="_blank">Clique aqui</a>

It will show a notification, depending on the browser , test this , like here:

Chrome by default already has Flash installed and updated by default, but off, unless you manually remove it . Other browsers may not even have access to Flash, this same link will point to the Flash download page.