gistfile1.html

<script>
function AppViewModel() {
    this.firstName = "Bert";
    this.lastName = "Bertington";
}

ko.applyBindings(new AppViewModel());
</script>

<p>First name: <strong data-bind="text: firstName"></strong></p>
<p>Last name: <strong data-bind="text: lastName"></strong></p>

gistfile1.js

<script>
function AppViewModel() {
    this.firstName = "Bert";
    this.lastName = "Bertington";
}

ko.applyBindings(new AppViewModel());
</script>

<p>First name: <strong data-bind="text: firstName"></strong></p>
<p>Last name: <strong data-bind="text: lastName"></strong></p>