KO get observable value before change

HTML

<span type="text" data-bind="text: Note"></span>

JavaScript

function ViewModel(){
    var self = this;
    
    self.Note = ko.observable("Test1");
    self.Note = ko.observable("Test2");
    
    self.Note.subscribe(function(oldValue) {
        console.log(oldValue);
    }, self, "beforeChange");
}

ko.applyBindings(new ViewModel());