I got errors when I used the syntax of the old angularfire2 version as I have the latest version(angularfire2 version 4.0.0) installed. Hence, instead of updating my knowledge I'd prefer to degrade to the lower version(angularfire2 version 2.0.0) so that my program will work fine. How do I do this?
You can uninstall the older version of angularfire2.
npm uninstall angularfire2 --save
To install any particular version, use @.
npm install angularfire2@2.0.0 --save
save option sets it in your package.json