Knockout - Moment - underscore - date filter grouping - JSFiddle
HTML
<script src="https://raw.github.com/timrwood/moment/1.6.2/min/moment.min.js"></script>
<script src="http://underscorejs.org/underscore-min.js"></script>
JavaScript
var answer = inRange(moment().isoWeekday(), 1, 5)
alert(answer)