IE 8 not working

by nickkell

HTML

<script src="http://knockoutjs.com/downloads/knockout-2.2.1.debug.js"></script>
<label><b>Client code</b>

    <select data-bind="options: ['code'], value: allpayAccountSearchParameters.scheme"></select>
</label>
<label> <b>Last Name</b>

    <input name="LastName" type="text" data-bind="value: allpayAccountSearchParameters.lastName, valueUpdate:'onkeyup'" />
</label>
<label for="Reference"> <b>Reference</b>

    <input name="Reference" type="text" data-bind="value: allpayAccountSearchParameters.reference, valueUpdate:'onkeyup'" />
</label>
<input type="button" data-bind="click: nextPage" value="next" />
<p data-bind="text: allpayAccountSearchParameters.sufficientInputToSearchForAccount"></p>
<p data-bind="text: 'Page: ' + page().index"></p>

JavaScript

var Page = (function () {
    function Page(index, name, canNavigateToPage, navigatedToThisPage) {
        this.index = index;
        this.name = name;
        this.canNavigateToPage = canNavigateToPage;
        this.navigatedToThisPage = navigatedToThisPage;
    }
    Page.prototype.navigateToPage = function () {
        if (this.canNavigateToPage()) {
            this.navigatedToThisPage(this);
        }
    };
    return Page;
})();

var AllpayAccountSearchParameters = (function () {
    function AllpayAccountSearchParameters() {
        this.reference = ko.observable();
        this.scheme = ko.observable();
        this.lastName = ko.observable();
        this.sufficientInputToSearchForAccount = ko.computed(function () {

            return this.reference() && this.scheme() && this.lastName();
        }, this);
    }
    return AllpayAccountSearchParameters;
})();

function viewModel() {
    var self = this,
        currentPage = ko.observable(),
        allpayAccountSearchParameters = new AllpayAccountSearchParameters(),
        forwardPageProgressionGuards = {
            '1': function canMoveToPage2() {
                console.log(allpayAccountSearchParameters.sufficientInputToSearchForAccount());
                return allpayAccountSearchParameters.sufficientInputToSearchForAccount();
            },
                '2': function canMoveToPage3() {
                return true;
            },
                '3': function canMoveToPage4() {
                return true;
            }
        },
        canMoveToNextPage = function (currentlyOnPage) {
            function disallowPageMovementNotExplicitlyDefined() {
                return false;
            }

            return (forwardPageProgressionGuards[currentlyOnPage] || disallowPageMovementNotExplicitlyDefined)();
        },
        canMoveToPreviousPage = function (currentlyOnPage) {
            return currentlyOnPage > 1;
        },
        pages = [
        new Page(1, 'Customer details',...