Knockout Log/Logger Binding Handler

logChange.js

//- for testing (logchange)
ko.extenders.logChange = function (target, option) {
    target.subscribe(function (newValue) {
        console.log(option + " : " + newValue);
    });
    return target;
};

ko.bindingHandlers.logger = {
    update: function (element, valueAccessor, allBindings) {
        //store a counter with this element
        var count = ko.utils.domData.get(element, "_ko_logger") || 0,
            data = ko.toJS(valueAccessor() || allBindings());

        ko.utils.domData.set(element, "_ko_logger", ++count);

        if (window.console && console.log) {
            console.log(count, element, data);
        }
    }
};