Why is this instance known to the javascript function
<p>How can it be that the sampleViewModel instance in the addChangedValue function is not undefined or null ?</p>

<p>From the scope of instantiation the sampleViewModel should not be known in the addChangedValue function as far my understanding is.</p>

<pre><code>$(function(){

    var PersonViewModel = function() {
        var me = this;
        me.firstName = ko.observable('Lisa'),
        me.lastName = ko.observable('T'),
        me.changes = ko.observableArray()
    };

    var sampleViewModel = new PersonViewModel();

    sampleViewModel.firstName.subscribe(function(newValue) {
        addChangedValue("firstname refreshed: " + newValue);
    });

    function addChangedValue(updatedValue) {
        sampleViewModel.changes.push({ value: updatedValue });
    };

    ko.applyBindings(sampleViewModel, document.getElementById('data'));
});
</code></pre>
