How subscribe on 'beforechange' event ?

[deadbit-dev]

I found this way addBinding(...).controller.value.emitter.on('beforechange', () => ...)
But why not possible just addBinding(...).on('beforechange', () => ...) ?

[2mik]

Hello,
I thought to ask a close question. Probably, I could ask in this issue.
To implement a history feature, we need to get an old value of a property before change. However, it would be more handy to get new and old values in a single event on binding change.

Is it possible to get an old value in the current version? If not, this is a feature request.