JSFiddle - React, Tailwind, and code Playground

HTML

<span class="areas" data-bind="foreach: areas">
    <label><input type="checkbox" data-bind="value: AreaId, checked: $parent.AreasImpacted.indexOf(AreaId) >= 0" /><span data-bind="text: Name"></span></label>
    <br />
</span>

JavaScript

3var ViewModel = function ()
{
   this.areas = [{AreaId: 1, Name: 'Test 1'}, {AreaId: 2, Name: 'Test 2'}, {AreaId: 3, Name: 'Test 3'}];
   this.AreasImpacted = ko.observableArray([1, 2]);
};

ko.applyBindings(new ViewModel());