just see the two approach and tell me what is the difference. when which one should use ? in first case instance will be created but in second case no instance will be created at the time of ko.applyBindings() so here is the code.
function MyViewModel() { var self = this; self.lastInterest = ko.observable(); self.places = ko.observableArray(['London', 'Paris', 'Tokyo']); // The current item will be passed as the first parameter, so we know which place was hovered over self.logMouseOver = function(place) { self.lastInterest(place); } } ko.applyBindings(new MyViewModel()); var viewModel = { detailsEnabled: ko.observable(false), enableDetails: function() { this.detailsEnabled(true); }, disableDetails: function() { this.detailsEnabled(false); } }; ko.applyBindings(viewModel); 
