isInteger issue with Internet Explorer

I’m gettinga dugger error in IE10, any help appreciated:

SCRIPT438: Object doesn’t support property or method ‘isInteger’
property.js (8,9)

function flattenFilters(link, page) {
current_page = Number.isInteger(page) ? page : 1; // reset page to initial if not passed in
var filters = link.data(‘filters’),
string = ‘[property_overview sorter=on sorter_type=none pagination=off per_page=12 ‘;
string += filters;
string += ‘ sale_status=’;
string += (window.location.href.indexOf(“sold-properties”) > -1) ? “Sold” : “Sale,Auction”;
string += ‘ starting_row=’;
string += getStartingRow();
string += ‘ template=custom-grid]’;
return string;
}

The page I need help with: [log in to see the link]