Knockout-2.2.0, subscribe get value before change AND new value

Question

jsfiddle link: http://jsfiddle.net/T8ee7/

When I call Knockout\'s subscribe method is there a way I can get both the previous and new value? Right now, I can only call g

Answer 1

http://jsfiddle.net/MV3fN/3/

var sv = sv || {};
sv.PagedRequest = function (pageNumber, pageSize) {
    var self = this;
    self.pageNumber = ko.observable(pageNumber || 1);
    self.numberOfPages = ko.observable(1);
    self.pageSize = ko.observable(pageSize || sv.DefaultPageSize);

    self.pageNumber.subscribe(function (previousValue) {
        console.log(previousValue);
        console.log(self.pageNumber.arguments[0]);
        if (previousValue != _pagedRequest.pageNumber.arguments[0]) {
            console.log('value changed');
        } 
        else {
            //This won't get executed because KO doesn't
            //call the function if the value doesn't change
            console.log('not changed');
        }
    }, _pagedRequest, "beforeChange");
};

var _pagedRequest = new sv.PagedRequest();

_pagedRequest.pageNumber(10);
_pagedRequest.pageNumber(20);
_pagedRequest.pageNumber(20);
_pagedRequest.pageNumber(5);

I don't know if you're really supposed to use arguments[0], but it seems to work.

You could also set up your own method to accomplish this in a much cleaner way:

http://jsfiddle.net/PXKgr/2/

...
    self.setPageNumber = function(page) {
        console.log(self.pageNumber());
        console.log(page);
        if (self.pageNumber() != page) {
            console.log('value changed');
        }
        else {
            console.log('not changed');
        }
        self.pageNumber(page);
    };
...
_pagedRequest.setPageNumber(10);
_pagedRequest.setPageNumber(20);
_pagedRequest.setPageNumber(20);
_pagedRequest.setPageNumber(5);