Example which I am using when I want to see which model I am sending to knockout. 

HTML:

    <body>
        <div data-bind="text: function() {debugger; return myText}()"></div>
    </body>

JS:

/*global ko*/
(function () {
    "use strict";
    function MyModel() {
        var self = this;

        self.myText = ko.observable("Test");
    }

    MyModel = new MyModel();
    ko.applyBindings(MyModel);
}());

Notice in HTML line:

<div data-bind="text: function() {debugger; return myText}()"></div>

In that line you can see debugger, and also return, which will force function to return value. Now you can debug knockout.