Select2.js

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/select2/3.3.2/select2.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/knockout/2.2.1/knockout-min.js"></script>
<select data-bind="options: options, optionsText: 'optionsText', optionsValue:'optionsValue'"></select>

JavaScript

$(function () {
    var vm = new viewModel();
    ko.applyBindings(vm);
    $("select").select2();
});


function viewModel() {
    var self = this;
    self.options = ko.observableArray(
    [{
        optionsValue: 1,
        optionsText: "One"
    }, {
        optionsValue: 2,
        optionsText: "two"
    }, {
        optionsValue: 3,
        optionsText: "three"
    }]);
}