<form data-bind="submit: doSomething">
... form contents go here ...
<button type="submit">Submit</button>
</form>
<script type="text/javascript">
var viewModel = {
doSomething : function(formElement) {
// ... now do something
}
};
</script>

<p>
<input type='checkbox' data-bind="checked: hasCellphone" />
I have a cellphone
</p>
<p>
Your cellphone number:
<input type='text' data-bind="value: cellphoneNumber, enable: hasCellphone" />
</p>
<script type="text/javascript">
var viewModel = {
hasCellphone : ko.observable(false),
cellphoneNumber: ""
};
</script>